Hopper: java.lang.ClassCastException: wu cannot be cast to bam

java.lang.ClassCastException: wu cannot be cast to bam
	at bak.a(SourceFile:176)
	at azw.b(SourceFile:515)
	at bak.b(SourceFile:412)
	at ayw.d(SourceFile:143)
	at bak.d(SourceFile:489)
	at ayw.m(SourceFile:110)

---- Minecraft Crash Report ----
// Would you like a cupcake?

Time: 06.09.13 18:13
Description: Updating screen events

java.lang.ClassCastException: wu cannot be cast to bam
	at bak.a(SourceFile:176)
	at azw.b(SourceFile:515)
	at bak.b(SourceFile:412)
	at ayw.d(SourceFile:143)
	at bak.d(SourceFile:489)
	at ayw.m(SourceFile:110)
	at awb.m(SourceFile:1202)
	at awb.V(SourceFile:686)
	at awb.e(SourceFile:642)
	at net.minecraft.client.main.Main.main(SourceFile:103)


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

-- Head --
Stacktrace:
	at bak.a(SourceFile:176)
	at azw.b(SourceFile:515)
	at bak.b(SourceFile:412)
	at ayw.d(SourceFile:143)
	at bak.d(SourceFile:489)
	at ayw.m(SourceFile:110)

-- Affected screen --
Details:
	Screen name: bak

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bfn['Derkecksfresser'/27106, l='MpServer', x=220,32, y=63,62, z=-1056,44]]
	Chunk stats: MultiplayerChunkCache: 288, 288
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-161,64,255), Chunk: (at 15,4,15 in -11,15; contains blocks -176,0,240 to -161,255,255), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
	Level time: 12879 game time, 12879 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: 42 total; [sd['Fledermaus'/30344, l='MpServer', x=149,75, y=18,00, z=-995,25], sd['Fledermaus'/31096, l='MpServer', x=146,31, y=15,00, z=-1013,94], sd['Fledermaus'/31097, l='MpServer', x=154,59, y=18,18, z=-996,69], tl['entity.MinecartChest.name'/27223, l='MpServer', x=301,50, y=20,50, z=-1129,50], bfn['Derkecksfresser'/27106, l='MpServer', x=220,32, y=63,62, z=-1056,44], sg['Kuh'/27227, l='MpServer', x=292,50, y=70,00, z=-1085,81], sg['Kuh'/27226, l='MpServer', x=294,16, y=70,00, z=-1075,91], sg['Kuh'/27225, l='MpServer', x=294,69, y=70,00, z=-1080,06], sg['Kuh'/27224, l='MpServer', x=294,59, y=70,00, z=-1078,31], sr['Tintenfisch'/27130, l='MpServer', x=161,47, y=50,34, z=-1111,84], sg['Kuh'/27206, l='MpServer', x=266,50, y=63,00, z=-980,50], sg['Kuh'/27207, l='MpServer', x=261,28, y=67,00, z=-986,50], sr['Tintenfisch'/27204, l='MpServer', x=262,31, y=55,38, z=-1021,84], sg['Kuh'/27205, l='MpServer', x=264,50, y=63,00, z=-980,50], sr['Tintenfisch'/27129, l='MpServer', x=163,63, y=50,31, z=-1117,56], sr['Tintenfisch'/27202, l='MpServer', x=260,88, y=56,38, z=-1026,81], sd['Fledermaus'/27339, l='MpServer', x=293,50, y=25,00, z=-1054,97], sr['Tintenfisch'/27203, l='MpServer', x=262,50, y=56,34, z=-1035,50], sd['Fledermaus'/27135, l='MpServer', x=163,25, y=31,10, z=-993,25], sd['Fledermaus'/27338, l='MpServer', x=288,75, y=24,00, z=-1054,50], sd['Fledermaus'/27337, l='MpServer', x=271,94, y=24,71, z=-1044,97], sd['Fledermaus'/27336, l='MpServer', x=280,13, y=23,52, z=-1048,09], sr['Tintenfisch'/27201, l='MpServer', x=268,50, y=55,00, z=-1027,50], sd['Fledermaus'/27133, l='MpServer', x=160,06, y=23,16, z=-1051,25], sd['Fledermaus'/27186, l='MpServer', x=228,53, y=41,10, z=-1026,50], sd['Fledermaus'/27188, l='MpServer', x=233,25, y=15,10, z=-997,44], sd['Fledermaus'/27555, l='MpServer', x=299,69, y=44,10, z=-1071,69], sd['Fledermaus'/27193, l='MpServer', x=244,49, y=13,37, z=-998,52], sr['Tintenfisch'/27169, l='MpServer', x=211,27, y=59,00, z=-1078,68], sr['Tintenfisch'/27170, l='MpServer', x=219,25, y=60,47, z=-1079,85], sr['Tintenfisch'/27171, l='MpServer', x=212,45, y=58,00, z=-1085,41], sr['Tintenfisch'/27172, l='MpServer', x=219,53, y=59,00, z=-1083,53], sg['Kuh'/27173, l='MpServer', x=218,50, y=69,00, z=-1069,25], sg['Kuh'/27174, l='MpServer', x=211,84, y=68,00, z=-1069,63], sg['Kuh'/27175, l='MpServer', x=199,51, y=68,00, z=-1076,59], sg['Kuh'/27176, l='MpServer', x=213,88, y=71,00, z=-1064,47], sr['Tintenfisch'/27178, l='MpServer', x=218,63, y=59,97, z=-1010,09], sr['Tintenfisch'/27158, l='MpServer', x=193,34, y=55,13, z=-1105,25], sr['Tintenfisch'/27157, l='MpServer', x=198,25, y=53,06, z=-1103,84], sr['Tintenfisch'/27156, l='MpServer', x=195,13, y=56,38, z=-1113,81], sr['Tintenfisch'/27140, l='MpServer', x=186,88, y=52,00, z=-1102,88], sr['Tintenfisch'/27141, l='MpServer', x=187,56, y=55,34, z=-1104,25]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bfi.a(SourceFile:285)
	at awb.b(SourceFile:1813)
	at awb.e(SourceFile:651)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 13w36b
	Operating System: Mac OS X (x86_64) version 10.6.8
	Java Version: 1.6.0_51, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 57493840 bytes (54 MB) / 278310912 bytes (265 MB) up to 1069416448 bytes (1019 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 528 (29568 bytes; 0 MB) allocated, 2 (112 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
	Launched Version: 13w36b
	LWJGL: 2.9.0
	OpenGL: ATI Radeon HD 4670 OpenGL Engine GL version 2.1 ATI-1.6.36, ATI Technologies Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: []
	Current Language: Deutsch (Deutschland)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 3018 (169008 bytes; 0 MB) allocated, 20 (1120 bytes; 0 MB) used