I don't know if this is entirely your fault or a conflict with another mod, but it pointed to OpenComputers first, so here is a crash report I got when I tried to kill a sheep:
---- Minecraft Crash Report ----

WARNING: coremods are present:
CCLCorePlugin (CodeChickenLib-1.8-1.1.2.115-universal.jar)
TransformerLoader (OpenComputers-MC1.8-1.5.4.9-universal.jar)
CCCDeobfPlugin (unknown)
CodeChickenCorePlugin (CodeChickenCore-1.8-1.0.5.34-universal.jar)
NEICorePlugin (NotEnoughItems-1.8-1.0.5.88-universal.jar)
ItemPatchingLoader (ItemPhysic Full 1.1.4 mc1.8.jar)
NowWithRendering (hopperducts-mc1.8-1.4.5.jar)
LoadingPlugin (VersionChecker-1.2.1.jar)
keysoverhaul (KeyBindingsOverhaul-LATEST-1.8.jar)
Contact their authors BEFORE contacting forge

// I just don't know what went wrong :(

Time: 3/30/15 4:31 PM
Description: Unexpected error

java.lang.NullPointerException: Unexpected error
at li.cil.oc.util.BlockPosition$.apply(BlockPosition.scala:52)
at li.cil.oc.client.renderer.HighlightRenderer$.onDrawBlockHighlight(HighlightRenderer.scala:34)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_33_HighlightRenderer$_onDrawBlockHighlight_DrawBlockHighlightEvent.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:55)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:138)
at net.minecraftforge.client.ForgeHooksClient.onDrawBlockHighlight(ForgeHooksClient.java:271)
at net.minecraft.client.renderer.EntityRenderer.func_175068_a(EntityRenderer.java:1321)
at net.minecraft.client.renderer.EntityRenderer.func_78471_a(EntityRenderer.java:1207)
at net.minecraft.client.renderer.EntityRenderer.func_78480_b(EntityRenderer.java:1032)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1048)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:345)
at net.minecraft.client.main.Main.main(SourceFile:120)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Stacktrace:
at li.cil.oc.util.BlockPosition$.apply(BlockPosition.scala:52)
at li.cil.oc.client.renderer.HighlightRenderer$.onDrawBlockHighlight(HighlightRenderer.scala:34)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_33_HighlightRenderer$_onDrawBlockHighlight_DrawBlockHighlightEvent.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:55)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:138)
at net.minecraftforge.client.ForgeHooksClient.onDrawBlockHighlight(ForgeHooksClient.java:271)
at net.minecraft.client.renderer.EntityRenderer.func_175068_a(EntityRenderer.java:1321)
at net.minecraft.client.renderer.EntityRenderer.func_78471_a(EntityRenderer.java:1207)

-- Affected level --
Details:
Level name: MpServer
All players: 1 total; [EntityPlayerSP['The_Fireplace'/163, l='MpServer', x=258.93, y=67.00, z=247.85]]
Chunk stats: MultiplayerChunkCache: 270, 270
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: 240.00,64.00,252.00 - World: (240,64,252), Chunk: (at 0,4,12 in 15,15; contains blocks 240,0,240 to 255,255,255), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 1562 game time, 1562 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Forced entities: 71 total; [EntitySheep['Sheep'/40, l='MpServer', x=250.34, y=66.00, z=229.75], EntitySheep['Sheep'/41, l='MpServer', x=259.09, y=67.00, z=243.16], EntitySheep['Sheep'/42, l='MpServer', x=246.13, y=66.00, z=238.25], EntitySheep['Sheep'/43, l='MpServer', x=265.91, y=67.00, z=253.00], EntitySheep['Sheep'/44, l='MpServer', x=239.50, y=64.00, z=253.75], EntitySheep['Sheep'/45, l='MpServer', x=262.16, y=67.00, z=247.34], EntitySheep['Sheep'/46, l='MpServer', x=253.50, y=64.00, z=262.81], EntitySheep['Sheep'/47, l='MpServer', x=246.56, y=64.00, z=257.63], EntityItem['item.tile.flower2.houstonia'/56, l='MpServer', x=262.84, y=19.00, z=196.94], EntityItem['item.tile.flower2.houstonia'/57, l='MpServer', x=261.56, y=19.00, z=195.75], EntityChicken['Chicken'/58, l='MpServer', x=278.38, y=73.00, z=327.50], EntityChicken['Chicken'/59, l='MpServer', x=267.50, y=73.00, z=325.50], EntityChicken['Chicken'/60, l='MpServer', x=277.25, y=73.00, z=327.50], EntityChicken['Chicken'/61, l='MpServer', x=272.50, y=70.00, z=324.50], EntityCreeper['Creeper'/6213, l='MpServer', x=337.50, y=48.00, z=293.50], EntitySkeleton['Skeleton'/6215, l='MpServer', x=225.50, y=26.00, z=235.50], EntityCow['Cow'/74, l='MpServer', x=281.78, y=63.00, z=306.78], EntityCow['Cow'/75, l='MpServer', x=281.19, y=64.00, z=313.59], EntitySheep['Sheep'/91, l='MpServer', x=303.50, y=67.00, z=191.50], EntitySheep['Sheep'/92, l='MpServer', x=307.81, y=67.00, z=194.69], EntitySheep['Sheep'/93, l='MpServer', x=312.91, y=67.00, z=201.03], EntitySheep['Sheep'/94, l='MpServer', x=303.16, y=67.00, z=194.81], EntityChicken['Chicken'/100, l='MpServer', x=336.50, y=72.00, z=273.50], EntityChicken['Chicken'/101, l='MpServer', x=334.53, y=72.00, z=283.34], EntityChicken['Chicken'/102, l='MpServer', x=336.50, y=72.00, z=274.50], EntityRabbit['Rabbit'/103, l='MpServer', x=329.50, y=65.00, z=323.50], EntityRabbit['Rabbit'/104, l='MpServer', x=330.47, y=69.00, z=318.81], EntityRabbit['Rabbit'/105, l='MpServer', x=329.34, y=64.00, z=326.34], EntityEnderman['Enderman'/6359, l='MpServer', x=265.56, y=11.00, z=259.47], EntityBat['Bat'/8407, l='MpServer', x=201.84, y=27.00, z=189.75], EntityCreeper['Creeper'/6360, l='MpServer', x=273.00, y=11.00, z=255.41], EntityBat['Bat'/8408, l='MpServer', x=211.22, y=27.19, z=208.84], EntityCreeper['Creeper'/6361, l='MpServer', x=270.59, y=11.00, z=259.00], EntityBat['Bat'/8409, l='MpServer', x=197.31, y=27.28, z=174.41], EntityZombie['Zombie'/6362, l='MpServer', x=271.50, y=11.00, z=255.50], EntityBat['Bat'/8413, l='MpServer', x=198.56, y=26.02, z=176.25], EntityBat['Bat'/8414, l='MpServer', x=255.75, y=24.00, z=273.25], EntityBat['Bat'/8416, l='MpServer', x=266.16, y=27.69, z=267.13], EntityBat['Bat'/8418, l='MpServer', x=241.03, y=15.09, z=280.88], EntityBat['Bat'/8419, l='MpServer', x=237.44, y=16.10, z=279.25], EntityZombie['Zombie'/8441, l='MpServer', x=204.34, y=22.00, z=302.34], EntityCreeper['Creeper'/8480, l='MpServer', x=266.69, y=11.00, z=259.50], EntityCreeper['Creeper'/8481, l='MpServer', x=267.59, y=11.00, z=259.50], EntityZombie['Zombie'/8482, l='MpServer', x=268.50, y=11.00, z=259.50], EntityZombie['Zombie'/8507, l='MpServer', x=176.66, y=22.00, z=269.69], EntityPlayerSP['The_Fireplace'/163, l='MpServer', x=258.93, y=67.00, z=247.85], EntityCreeper['Creeper'/385, l='MpServer', x=257.50, y=31.00, z=249.50], EntitySkeleton['Skeleton'/388, l='MpServer', x=307.50, y=14.00, z=311.50], EntitySkeleton['Skeleton'/438, l='MpServer', x=201.50, y=33.00, z=179.50], EntityBat['Bat'/487, l='MpServer', x=228.01, y=18.16, z=272.57], EntityZombie['Zombie'/8852, l='MpServer', x=186.50, y=21.00, z=282.50], EntityCreeper['Creeper'/8854, l='MpServer', x=227.50, y=42.00, z=174.50], EntityZombie['Zombie'/6928, l='MpServer', x=329.72, y=21.00, z=303.16], EntitySpider['Spider'/6930, l='MpServer', x=338.50, y=22.00, z=298.50], EntityBat['Bat'/6978, l='MpServer', x=308.25, y=11.00, z=275.44], EntitySkeleton['Skeleton'/7161, l='MpServer', x=179.50, y=21.00, z=269.50], EntityZombie['Zombie'/7174, l='MpServer', x=294.50, y=10.00, z=279.50], EntitySpider['Spider'/7233, l='MpServer', x=195.50, y=37.00, z=169.50], EntitySpider['Spider'/7234, l='MpServer', x=191.50, y=37.00, z=168.50], EntityZombie['Zombie'/1118, l='MpServer', x=332.50, y=60.00, z=287.50], EntitySkeleton['Skeleton'/7455, l='MpServer', x=175.50, y=23.00, z=183.50], EntitySpider['Spider'/7488, l='MpServer', x=269.50, y=27.00, z=261.50], EntitySpider['Spider'/7489, l='MpServer', x=267.50, y=27.00, z=264.50], EntityZombie['Zombie'/7743, l='MpServer', x=177.50, y=22.00, z=268.50], EntityZombie['Zombie'/7744, l='MpServer', x=178.34, y=21.00, z=270.06], EntitySkeleton['Skeleton'/1604, l='MpServer', x=192.50, y=28.00, z=181.50], EntityZombie['Zombie'/1616, l='MpServer', x=212.50, y=25.00, z=277.50], EntityCreeper['Creeper'/1625, l='MpServer', x=266.44, y=33.00, z=214.41], EntityZombie['Zombie'/1648, l='MpServer', x=336.50, y=26.00, z=279.50], EntityZombie['Zombie'/1715, l='MpServer', x=210.50, y=20.00, z=180.91], EntityBat['Bat'/6026, l='MpServer', x=275.00, y=20.00, z=189.84]]
Retry entities: 0 total; []
Server brand: fml,forge
Server type: Integrated singleplayer server
Stacktrace:
at net.minecraft.client.multiplayer.WorldClient.func_72914_a(WorldClient.java:351)
at net.minecraft.client.Minecraft.func_71396_d(Minecraft.java:2488)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:374)
at net.minecraft.client.main.Main.main(SourceFile:120)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
Minecraft Version: 1.8
Operating System: Windows 7 (x86) version 6.1
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 193483448 bytes (184 MB) / 523501568 bytes (499 MB) up to 523501568 bytes (499 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
FML: MCP v9.10 FML v8.0.42.1338 Minecraft Forge 11.14.1.1338 32 mods loaded, 32 mods active
mcp{9.05} Minecraft Coder Pack Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
FML{8.0.42.1338} Forge Mod Loader Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Forge{11.14.1.1338} Minecraft Forge Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
CodeChickenCore{1.0.5.34} CodeChicken Core Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
NotEnoughItems{1.0.5.88} Not Enough Items Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
OpenComputers|Core{1.0.0} OpenComputers (Core) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
itemphysic{1.1.2} ItemPhysic Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
securitycraft{v1.7.3} [SecurityCraft]([1.8] SecurityCraft 1.7.3.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
basemetals{1.2.1} Base Metals Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
info.varden.chatlog{2.1.1.43} ChatLog Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
lootablebodies{1.1.2} DrCyano's Lootable Bodies Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
VersionChecker{1.2.1} Version Checker Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
fireplacecore{2.1.4.0} [Fireplace Core](Fireplace Core 2.1.4.0.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
clayspawn{2.0.2.0} [Fire's Clay Spawn](Fire's Clay Spawn 2.0.2.0.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
glass_shards{1.3.1} Glass Shards Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
hopperducts{1.4.5} Hopper Ducts Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
IngameAccountSwitcher{1.8-r1} In-Game Account Switcher Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
keysoverhaul{1.0} Key Bindings Overhaul Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
LavaBoat{2.1.0} LavaBoat Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
mobrebirth{2.1.0.4} [Mob Rebirth](Mob Rebirth 2.1.0.4.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
moreclienttweaks{2.0.0.3} [More Client Tweaks](More Client Tweaks 2.0.0.3.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
antiswear{2.0.0.3} [More Client Tweaks - AntiSwear Module](More Client Tweaks 2.0.0.3.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
neotech{1.5} NeoTech Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
netheressence{2.0.0.1} [Nether Essence](Nether Essence 2.0.0.1.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
OpenComputers{1.5.4.9} OpenComputers Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
parachutemod{1.8.0} Parachute Mod Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
PigManure{1.0.1} Pig Manure Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
progressiveautomation{1.6.4} Progressive Automation Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
shipwrecks_winslow{1.6.3} Shipwrecks! Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
SlimevoidLib{3.0.0.4-beta-1.8} Slimevoid Library Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
WirelessRedstone{2.0.0.1-alpha-1.8} Wireless Redstone Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
XaeroMinimap{1.3.9} Xaero's Minimap Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Loaded coremods (and transformers):
CCLCorePlugin (CodeChickenLib-1.8-1.1.2.115-universal.jar)
codechicken.lib.asm.ClassHeirachyManager
codechicken.lib.asm.RenderHookTransformer
TransformerLoader (OpenComputers-MC1.8-1.5.4.9-universal.jar)
li.cil.oc.common.asm.ClassTransformer
CCCDeobfPlugin (unknown)

CodeChickenCorePlugin (CodeChickenCore-1.8-1.0.5.34-universal.jar)
codechicken.core.asm.InterfaceDependancyTransformer
codechicken.core.asm.TweakTransformer
codechicken.core.asm.DelegatedTransformer
codechicken.core.asm.DefaultImplementationTransformer
NEICorePlugin (NotEnoughItems-1.8-1.0.5.88-universal.jar)
codechicken.nei.asm.NEITransformer
ItemPatchingLoader (ItemPhysic Full 1.1.4 mc1.8.jar)
com.creativemd.itemphysic.ItemTransformer
NowWithRendering (hopperducts-mc1.8-1.4.5.jar)
net.fybertech.nwr.NowWithRendering
LoadingPlugin (VersionChecker-1.2.1.jar)

keysoverhaul (KeyBindingsOverhaul-LATEST-1.8.jar)
code.elix_x.coremods.keysoverhaul.core.KeysOverhaulTransformer
Launched Version: 1.8-Forge11.14.1.1338
LWJGL: 2.9.1
OpenGL: GeForce GT 620/PCIe/SSE2 GL version 4.5.0 NVIDIA 347.88, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: No
Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)