Game crashed while AFK

---- Minecraft Crash Report ----
// Oh - I know what I did wrong!

Time: 7/4/13 11:19 AM
Description: Rendering Tile Entity

java.lang.ClassCastException: asb cannot be cast to arr
	at arr.j(SourceFile:168)
	at bik.a(SourceFile:51)
	at bik.a(SourceFile:15)
	at bis.a(SourceFile:106)
	at bis.a(SourceFile:98)
	at bfa.a(SourceFile:324)
	at bet.a(SourceFile:845)
	at bet.b(SourceFile:695)
	at atn.S(SourceFile:685)
	at atn.d(SourceFile:618)
	at net.minecraft.client.main.Main.main(SourceFile:101)


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

-- Head --
Stacktrace:
	at arr.j(SourceFile:168)
	at bik.a(SourceFile:51)
	at bik.a(SourceFile:15)

-- Tile Entity Details --
Details:
	Name: Chest // arr
	Block type: ID #54 (tile.chest // and)
	Block data value: 3 / 0x3 / 0b0011
	Block location: World: (118,123,100), Chunk: (at 6,7,4 in 7,6; contains blocks 112,0,96 to 127,255,111), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Actual block type: ID #54 (tile.chest // and)
	Actual block data value: 3 / 0x3 / 0b0011
Stacktrace:
	at bis.a(SourceFile:106)
	at bis.a(SourceFile:98)
	at bfa.a(SourceFile:324)
	at bet.a(SourceFile:845)

-- Affected level --
Details:
	Level name: MpServer
	All players: 2 total; [bcx['Matthodgson'/401573, l='MpServer', x=107.32, y=122.62, z=105.40], ben['Feyerholm'/385699, l='MpServer', x=115.88, y=121.88, z=100.50]]
	Chunk stats: MultiplayerChunkCache: 121
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (996,63,885), Chunk: (at 4,3,5 in 62,55; contains blocks 992,0,880 to 1007,255,895), Region: (1,1; contains chunks 32,32 to 63,63, blocks 512,0,512 to 1023,255,1023)
	Level time: 8298994 game time, 8298994 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: creative (ID 1). Hardcore: false. Cheats: false
	Forced entities: 17 total; [sp['item.tile.sapling.oak'/428455, l='MpServer', x=110.19, y=119.13, z=110.19], tk['Zombie Pigman'/402057, l='MpServer', x=123.50, y=50.00, z=47.97], tk['Zombie Pigman'/402056, l='MpServer', x=130.59, y=60.00, z=39.38], sp['item.tile.sapling.oak'/428453, l='MpServer', x=112.19, y=121.13, z=109.66], sp['item.item.apple'/428452, l='MpServer', x=109.22, y=120.13, z=107.19], tk['Zombie Pigman'/402053, l='MpServer', x=98.88, y=50.00, z=47.66], sp['item.tile.sapling.oak'/428321, l='MpServer', x=108.88, y=118.13, z=109.72], ben['Feyerholm'/385699, l='MpServer', x=115.88, y=121.88, z=100.50], ti['Magma Cube'/402139, l='MpServer', x=47.97, y=23.00, z=162.22], sp['item.tile.sapling.oak'/428363, l='MpServer', x=112.56, y=121.13, z=107.19], ben['Feyerholm'/385699, l='MpServer', x=175.09, y=54.00, z=71.47], bcx['Matthodgson'/401573, l='MpServer', x=107.32, y=122.62, z=105.40], ben['TheMCArchitect'/402370, l='MpServer', x=174.86, y=56.84, z=79.49], ben['TheMCArchitect'/402370, l='MpServer', x=174.28, y=56.34, z=71.47], tk['Zombie Pigman'/403529, l='MpServer', x=134.50, y=91.00, z=45.50], tk['Zombie Pigman'/402043, l='MpServer', x=117.50, y=54.88, z=45.59], ben['Feyerholm'/385699, l='MpServer', x=115.88, y=121.88, z=100.50]]
	Retry entities: 0 total; []
Stacktrace:
	at bcu.a(SourceFile:284)
	at atn.b(SourceFile:1743)
	at atn.d(SourceFile:627)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.1
	Operating System: Mac OS X (x86_64) version 10.8.4
	Java Version: 1.6.0_51, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 76836968 bytes (73 MB) / 133611520 bytes (127 MB) up to 1065025536 bytes (1015 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 148 (8288 bytes; 0 MB) allocated, 144 (8064 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Launched Version: 1.6.1
	LWJGL: 2.9.0
	OpenGL: ATI Radeon HD 5670 OpenGL Engine GL version 2.1 ATI-1.8.18, ATI Technologies Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 6184 (346304 bytes; 0 MB) allocated, 64 (3584 bytes; 0 MB) used

I was AFK when this happened so I do not know what caused it to crash.