Put the summary of the bug you're having here

What I expected to happen was...:
I should have started playing in my world with no problems.

What actually happened was...:
When the world opened I was in the sky, frozen and unable to move. The screen went grey and everything locked up and then crashed to the error.

Steps to Reproduce:
Cant reproduce on demand.
Error is here.
Time: 12/01/14 09:01
Description: Rendering Block Entity

java.lang.ArrayIndexOutOfBoundsException: -13
at b.a(SourceFile:263)
at b.a(SourceFile:250)
at bqy.a(SourceFile:80)
at bqy.a(SourceFile:40)
at bne.a(SourceFile:17)
at bnk.a(SourceFile:43)
at bnk.a(SourceFile:12)
at bnd.a(SourceFile:100)
at bnd.a(SourceFile:92)
at bmt.a(SourceFile:383)
at bmm.a(SourceFile:994)
at bmm.b(SourceFile:814)
at azi.ah(SourceFile:787)
at azi.f(SourceFile:711)
at net.minecraft.client.main.Main.main(SourceFile:152)

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

– Head –
Stacktrace:
at b.a(SourceFile:263)
at b.a(SourceFile:250)
at bqy.a(SourceFile:80)
at bqy.a(SourceFile:40)
at bne.a(SourceFile:17)
at bnk.a(SourceFile:43)
at bnk.a(SourceFile:12)

– Block Entity Details –
Details:
Name: Sign // aod
Block type: ID #68 (tile.sign // amb)
Block data value: 2 / 0x2 / 0b0010
Block location: World: (-9,237,-10), Chunk: (at 7,14,6 in -1,-1; contains blocks -16,0,-16 to -1,255,-1), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Actual block type: ID #68 (tile.sign // amb)
Actual block data value: 2 / 0x2 / 0b0010
Stacktrace:
at bnd.a(SourceFile:100)
at bnd.a(SourceFile:92)
at bmt.a(SourceFile:383)
at bmm.a(SourceFile:994)

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [bkf['Killi7'/1620197, l='MpServer', x=-6.57, y=238.62, z=-11.75]]
Chunk stats: MultiplayerChunkCache: 5, 5
Level seed: 0
Level generator: ID 01 - flat, ver 0. Features enabled: false
Level generator options:
Level spawn location: World: (0,4,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 161388 game time, 161388 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: 13 total; [wb['item.item.egg'/1620155, l='MpServer', x=1.34, y=237.13, z=-6.97], wb['item.item.egg'/1620154, l='MpServer', x=2.88, y=237.13, z=-7.25], ux['Chicken'/1620153, l='MpServer', x=0.66, y=237.00, z=-7.66], ux['Chicken'/1620152, l='MpServer', x=0.16, y=237.00, z=-7.06], wb['item.item.egg'/1620156, l='MpServer', x=1.69, y=237.13, z=-5.75], vm['Wolf'/1620147, l='MpServer', x=9.72, y=237.00, z=-6.50], bkf['Killi7'/1620197, l='MpServer', x=-6.57, y=238.62, z=-11.75], vm['Wolf'/1620146, l='MpServer', x=7.78, y=237.00, z=-1.50], vm['Wolf'/1620145, l='MpServer', x=7.31, y=237.00, z=-6.25], ux['Chicken'/1620151, l='MpServer', x=0.56, y=237.00, z=-4.47], ux['Chicken'/1620150, l='MpServer', x=1.75, y=237.00, z=-6.19], vm['Wolf'/1620149, l='MpServer', x=15.34, y=237.00, z=-2.75], vm['Wolf'/1620148, l='MpServer', x=15.25, y=237.00, z=-7.50]]
Retry entities: 0 total; []
Server brand: vanilla
Server type: Integrated singleplayer server
Stacktrace:
at bka.a(SourceFile:289)
at azi.b(SourceFile:1952)
at azi.f(SourceFile:720)
at net.minecraft.client.main.Main.main(SourceFile:152)

– System Details –
Details:
Minecraft Version: 1.7.4
Operating System: Windows 7 (x86) version 6.1
Java Version: 1.7.0_45, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 1271744 bytes (1 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
AABB Pool Size: 30755 (1722280 bytes; 1 MB) allocated, 184 (10304 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 1.7.4
LWJGL: 2.9.1
OpenGL: GeForce GTX 650 Ti/PCIe/SSE2 GL version 4.3.0, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.

Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 219 (12264 bytes; 0 MB) allocated, 140 (7840 bytes; 0 MB) used
Anisotropic Filtering: Off (1)