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-190532/

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 axm.a(SourceFile:580)
	at awy.a(SourceFile:168)
	at axp.a(SourceFile:31)
	at axm.a(SourceFile:529)
	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 ----
// Daisy, daisy...

Time: 19/09/13 19:48
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 axm.a(SourceFile:580)
	at awy.a(SourceFile:168)
	at axp.a(SourceFile:31)
	at axm.a(SourceFile:529)
	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 axm.a(SourceFile:580)
	at awy.a(SourceFile:168)
	at axp.a(SourceFile:31)
	at axm.a(SourceFile:529)

-- Screen render details --
Details:
	Screen name: axm
	Mouse location: Scaled: (141, 171). Absolute: (282, 136)
	Screen size: Scaled: (427, 240). Absolute: (854, 480). Scale factor of 2

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bdi['Perseo517'/0, l='MpServer', x=908,93, y=57,62, z=1198,38]]
	Chunk stats: MultiplayerChunkCache: 441
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (907,4,1199), Chunk: (at 11,0,15 in 56,74; contains blocks 896,0,1184 to 911,255,1199), Region: (1,2; contains chunks 32,64 to 63,95, blocks 512,0,1024 to 1023,255,1535)
	Level time: 208157 game time, 42000 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: 1 total; [bdi['Perseo517'/0, l='MpServer', x=908,93, y=57,62, z=1198,38]]
	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 XP (x86) version 5.1
	Java Version: 1.7.0_07, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 119229288 bytes (113 MB) / 353968128 bytes (337 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 19635 (1099560 bytes; 1 MB) allocated, 27 (1512 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 1.6.4
	LWJGL: 2.9.0
	OpenGL: GeForce 7650 GS/PCI/SSE2 GL version 2.0.3, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: English (UK)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 79 (4424 bytes; 0 MB) allocated, 57 (3192 bytes; 0 MB) used

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-190532/12396524/