Hopper: java.lang.ClassCastException: cf cannot be cast to cj

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-192928/

Crash:

java.lang.ClassCastException: cf cannot be cast to cj
	at by.d(SourceFile:120)
	at ye.a(SourceFile:439)
	at awy.a(SourceFile:188)
	at awy.a(SourceFile:168)
	at axp.a(SourceFile:31)
	at axv.a(SourceFile:49)
	at bfe.b(SourceFile:718)
	at atv.S(SourceFile:686)
	at atv.d(SourceFile:619)
	at net.minecraft.client.main.Main.main(SourceFile:101)

The following is the first clean report made public about this crash:

---- Minecraft Crash Report ----
// Shall we play a game?

Time: 28/09/13 10:13 AM
Description: Reading NBT data

java.lang.ClassCastException: cf cannot be cast to cj
	at by.d(SourceFile:120)
	at ye.a(SourceFile:439)
	at awy.a(SourceFile:188)
	at awy.a(SourceFile:168)
	at axp.a(SourceFile:31)
	at axv.a(SourceFile:49)
	at bfe.b(SourceFile:718)
	at atv.S(SourceFile:686)
	at atv.d(SourceFile:619)
	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:
---------------------------------------------------------------------------------------

-- Corrupt NBT tag --
Details:
	Tag type found: INT
	Tag type expected: SHORT
	Tag name: id
Stacktrace:
	at by.d(SourceFile:120)
	at ye.a(SourceFile:439)
	at awy.a(SourceFile:188)
	at awy.a(SourceFile:168)
	at axp.a(SourceFile:31)
	at axv.a(SourceFile:49)

-- Screen render details --
Details:
	Screen name: axv
	Mouse location: Scaled: (321, 235). Absolute: (643, 235)
	Screen size: Scaled: (683, 353). Absolute: (1366, 706). Scale factor of 2

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bdi['minecraft0524'/201095, l='MpServer', x=884.53, y=57.62, z=304.30]]
	Chunk stats: MultiplayerChunkCache: 441
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (839,4,294), Chunk: (at 7,0,6 in 52,18; contains blocks 832,0,288 to 847,255,303), Region: (1,0; contains chunks 32,0 to 63,31, blocks 512,0,0 to 1023,255,511)
	Level time: 227734 game time, 10250 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: 56 total; [ss['item.tile.stone'/205531, l='MpServer', x=881.38, y=54.13, z=313.00], ss['item.tile.stone'/203705, l='MpServer', x=878.00, y=56.13, z=317.00], sy['entity.MinecartRideable.name'/201089, l='MpServer', x=877.54, y=56.55, z=304.93], sx['entity.MinecartHopper.name'/201088, l='MpServer', x=877.54, y=56.60, z=304.93], sx['entity.MinecartHopper.name'/201091, l='MpServer', x=879.49, y=56.60, z=303.51], sy['entity.MinecartRideable.name'/201090, l='MpServer', x=877.54, y=56.50, z=304.93], sy['entity.MinecartRideable.name'/201093, l='MpServer', x=879.49, y=56.50, z=303.51], sy['entity.MinecartRideable.name'/201092, l='MpServer', x=879.49, y=56.55, z=303.51], tf['Creeper'/201094, l='MpServer', x=905.50, y=18.00, z=305.50], ss['item.tile.stone'/204224, l='MpServer', x=880.00, y=56.13, z=317.00], ss['item.tile.stone'/202455, l='MpServer', x=877.00, y=56.13, z=314.00], ss['item.tile.stone'/206754, l='MpServer', x=882.00, y=56.13, z=310.00], ss['item.tile.stone'/204364, l='MpServer', x=881.00, y=56.13, z=317.00], ss['item.tile.stone'/205978, l='MpServer', x=881.28, y=54.15, z=312.00], ss['item.tile.stone'/201840, l='MpServer', x=877.00, y=56.13, z=312.00], ss['item.tile.stone'/203547, l='MpServer', x=877.00, y=56.13, z=317.00], ss['item.tile.stone'/202702, l='MpServer', x=877.00, y=56.13, z=315.00], ss['item.tile.stone'/206932, l='MpServer', x=882.00, y=56.77, z=310.00], ss['item.tile.stone'/203892, l='MpServer', x=879.00, y=56.13, z=317.00], ss['item.tile.stone'/206309, l='MpServer', x=881.20, y=54.13, z=311.00], ss['item.tile.stone'/207021, l='MpServer', x=882.00, y=57.13, z=309.00], ss['item.tile.stone'/206660, l='MpServer', x=882.00, y=56.13, z=310.00], ss['item.tile.stone'/201045, l='MpServer', x=874.69, y=56.13, z=303.00], ss['item.tile.stone'/202286, l='MpServer', x=877.00, y=56.13, z=313.00], sy['entity.MinecartRideable.name'/201047, l='MpServer', x=876.01, y=56.50, z=317.78], ss['item.tile.stone'/201053, l='MpServer', x=878.81, y=56.13, z=306.28], ss['item.tile.stone'/203085, l='MpServer', x=877.00, y=56.13, z=316.00], ss['item.tile.stone'/201052, l='MpServer', x=879.69, y=56.13, z=306.00], ss['item.tile.stone'/201055, l='MpServer', x=877.00, y=57.13, z=308.00], ss['item.tile.stone'/201054, l='MpServer', x=875.72, y=56.13, z=305.00], ss['item.tile.stone'/201049, l='MpServer', x=879.66, y=56.13, z=312.00], ss['item.tile.stone'/201048, l='MpServer', x=878.78, y=56.13, z=310.91], bdi['minecraft0524'/201095, l='MpServer', x=884.53, y=57.62, z=304.30], ss['item.tile.stone'/201051, l='MpServer', x=879.47, y=56.13, z=309.69], ss['item.tile.stone'/201050, l='MpServer', x=879.13, y=56.13, z=307.47], ss['item.tile.stone'/201063, l='MpServer', x=874.50, y=56.13, z=306.00], sy['entity.MinecartRideable.name'/201060, l='MpServer', x=882.50, y=56.54, z=310.36], sz['entity.MinecartSpawner.name'/201058, l='MpServer', x=882.50, y=56.64, z=310.36], sy['entity.MinecartRideable.name'/201059, l='MpServer', x=882.50, y=56.59, z=310.36], ss['item.tile.stone'/201056, l='MpServer', x=877.00, y=57.13, z=309.00], ss['item.tile.stone'/201057, l='MpServer', x=875.03, y=56.13, z=310.00], ss['item.tile.stone'/201068, l='MpServer', x=877.00, y=56.13, z=310.00], ss['item.tile.stone'/201066, l='MpServer', x=877.88, y=56.13, z=307.56], ss['item.tile.stone'/201065, l='MpServer', x=877.00, y=56.13, z=307.00], ss['item.tile.stone'/201079, l='MpServer', x=881.13, y=54.13, z=312.00], ss['item.tile.stone'/201078, l='MpServer', x=881.13, y=54.13, z=314.00], ss['item.tile.stone'/201077, l='MpServer', x=881.13, y=54.13, z=316.00], ss['item.tile.stone'/201076, l='MpServer', x=881.13, y=54.13, z=315.00], ss['item.tile.stone'/201075, l='MpServer', x=880.66, y=56.13, z=312.00], ss['item.tile.stone'/201074, l='MpServer', x=880.56, y=56.13, z=311.00], ss['item.tile.stone'/201073, l='MpServer', x=880.41, y=56.13, z=307.16], tf['Creeper'/201072, l='MpServer', x=889.50, y=8.00, z=309.50], ss['item.tile.stone'/201085, l='MpServer', x=880.50, y=56.13, z=305.00], ss['item.tile.stone'/201414, l='MpServer', x=877.00, y=56.13, z=311.00], ss['item.tile.stone'/201082, l='MpServer', x=881.13, y=54.13, z=310.13], ss['item.tile.stone'/201080, l='MpServer', x=881.13, y=54.13, z=311.00]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bdd.a(SourceFile:284)
	at atv.b(SourceFile:1761)
	at atv.d(SourceFile:628)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.4
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_21, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 131867080 bytes (125 MB) / 436469760 bytes (416 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 21638 (1211728 bytes; 1 MB) allocated, 1767 (98952 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Launched Version: 1.6.4
	LWJGL: 2.9.0
	OpenGL: Intel(R) HD Graphics 4000 GL version 3.3.0 - Build 8.15.10.2653, Intel
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: Canadian English (CA)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 322 (18032 bytes; 0 MB) allocated, 93 (5208 bytes; 0 MB) used

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-192928/14968071/