Hopper: java.lang.ClassCastException: bw cannot be cast to ci

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-30742/

Crash:

java.lang.ClassCastException: bw cannot be cast to ci
	at bx.d(SourceFile:120)
	at yd.a(SourceFile:439)
	at awv.a(SourceFile:188)
	at axj.a(SourceFile:580)
	at awv.a(SourceFile:168)
	at axm.a(SourceFile:31)
	at axj.a(SourceFile:529)
	at bfb.b(SourceFile:718)
	at ats.S(SourceFile:686)
	at ats.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 ----
// You should try our sister game, Minceraft!

Time: 11.08.2013 09:20
Description: Reading NBT data

java.lang.ClassCastException: cj cannot be cast to ci
	at bx.d(SourceFile:120)
	at yd.a(SourceFile:439)
	at awv.a(SourceFile:188)
	at axj.a(SourceFile:580)
	at awv.a(SourceFile:168)
	at axm.a(SourceFile:31)
	at axj.a(SourceFile:529)
	at bfb.b(SourceFile:718)
	at ats.S(SourceFile:686)
	at ats.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: STRING
	Tag type expected: SHORT
	Tag name: id
Stacktrace:
	at bx.d(SourceFile:120)
	at yd.a(SourceFile:439)
	at awv.a(SourceFile:188)
	at axj.a(SourceFile:580)
	at awv.a(SourceFile:168)
	at axm.a(SourceFile:31)
	at axj.a(SourceFile:529)

-- Screen render details --
Details:
	Screen name: axj
	Mouse location: Scaled: (247, 228). Absolute: (495, 255)
	Screen size: Scaled: (640, 356). Absolute: (1280, 712). Scale factor of 2

-- Affected level --
Details:
	Level name: MpServer
	All players: 2 total; [bdf['efekral1500'/509, l='MpServer', x=290,57, y=82,62, z=198,55], bev['yigitabi4444'/269, l='MpServer', x=293,44, y=84,34, z=192,78]]
	Chunk stats: MultiplayerChunkCache: 20
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (171,64,255), Chunk: (at 11,4,15 in 10,15; contains blocks 160,0,240 to 175,255,255), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 33215 game time, 33215 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: 33 total; [sb['Ahtapot'/71, l='MpServer', x=260,56, y=56,37, z=196,13], rp['Tavuk'/152, l='MpServer', x=335,50, y=85,00, z=234,50], sr['item.item.egg'/153, l='MpServer', x=332,63, y=84,13, z=233,06], rw['Leopar'/154, l='MpServer', x=328,53, y=80,00, z=227,00], tv['Zombi'/81, l='MpServer', x=280,50, y=33,00, z=235,50], sp['Tekne'/95, l='MpServer', x=298,75, y=63,35, z=203,75], te['Creeper'/149, l='MpServer', x=329,69, y=15,00, z=187,66], tq['İskelet'/150, l='MpServer', x=335,55, y=33,00, z=179,55], rw['Leopar'/151, l='MpServer', x=328,53, y=65,00, z=177,31], bev['yigitabi4444'/269, l='MpServer', x=293,44, y=84,34, z=192,78], ua['Köylü'/102, l='MpServer', x=297,31, y=63,00, z=212,59], sr['item.item.stick'/103, l='MpServer', x=303,13, y=61,13, z=212,41], ua['Köylü'/100, l='MpServer', x=302,66, y=60,51, z=205,38], ua['Köylü'/101, l='MpServer', x=301,04, y=63,00, z=197,01], ua['Köylü'/98, l='MpServer', x=302,94, y=63,00, z=204,66], ua['Köylü'/99, l='MpServer', x=302,47, y=63,00, z=196,78], sp['Tekne'/96, l='MpServer', x=296,75, y=63,63, z=206,75], ua['Köylü'/97, l='MpServer', x=300,47, y=63,00, z=199,25], ua['Köylü'/106, l='MpServer', x=294,51, y=64,00, z=211,01], ua['Köylü'/104, l='MpServer', x=295,07, y=63,00, z=211,66], ua['Köylü'/105, l='MpServer', x=294,01, y=64,00, z=211,69], rp['Tavuk'/119, l='MpServer', x=313,50, y=66,00, z=188,50], rp['Tavuk'/118, l='MpServer', x=312,50, y=65,00, z=188,50], rp['Tavuk'/117, l='MpServer', x=312,50, y=65,00, z=189,50], bev['yigitabi4444'/269, l='MpServer', x=293,44, y=84,34, z=192,78], ua['Köylü'/126, l='MpServer', x=308,38, y=63,00, z=214,28], ua['Köylü'/125, l='MpServer', x=316,32, y=64,00, z=204,04], ua['Köylü'/124, l='MpServer', x=309,72, y=63,00, z=203,50], ua['Köylü'/123, l='MpServer', x=316,38, y=63,00, z=203,38], bdf['efekral1500'/509, l='MpServer', x=290,57, y=82,62, z=198,55], sp['Tekne'/122, l='MpServer', x=310,25, y=63,35, z=200,75], sr['item.item.egg'/121, l='MpServer', x=316,78, y=68,13, z=187,00], sr['item.item.egg'/120, l='MpServer', x=313,44, y=66,13, z=190,44]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Non-integrated multiplayer server
Stacktrace:
	at bda.a(SourceFile:284)
	at ats.b(SourceFile:1761)
	at ats.d(SourceFile:628)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.2
	Operating System: Windows XP (x86) version 5.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 156017584 bytes (148 MB) / 278310912 bytes (265 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 13235 (741160 bytes; 0 MB) allocated, 385 (21560 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Launched Version: 1.6.2
	LWJGL: 2.9.0
	OpenGL: GeForce 9500 GT/PCI/SSE2 GL version 3.3.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: Türkçe (TR)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 1547 (86632 bytes; 0 MB) allocated, 581 (32536 bytes; 0 MB) used

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-30742/2040533/