Hopper: java.lang.ClassCastException: we cannot be cast to axo

java.lang.ClassCastException: we cannot be cast to axo
	at axm.a(SourceFile:177)
	at awy.b(SourceFile:515)
	at axm.b(SourceFile:411)
	at awe.d(SourceFile:132)
	at axm.d(SourceFile:488)
	at awe.m(SourceFile:107)

---- Minecraft Crash Report ----
// Don't be sad. I'll do better next time, I promise!

Time: 9/19/13 7:26 PM
Description: Updating screen events

java.lang.ClassCastException: we cannot be cast to axo
	at axm.a(SourceFile:177)
	at awy.b(SourceFile:515)
	at axm.b(SourceFile:411)
	at awe.d(SourceFile:132)
	at axm.d(SourceFile:488)
	at awe.m(SourceFile:107)
	at atv.k(SourceFile:1158)
	at atv.S(SourceFile:663)
	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:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at axm.a(SourceFile:177)
	at awy.b(SourceFile:515)
	at axm.b(SourceFile:411)
	at awe.d(SourceFile:132)
	at axm.d(SourceFile:488)
	at awe.m(SourceFile:107)

-- Affected screen --
Details:
	Screen name: axm

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bdi['bilakos96bill'/119313, l='MpServer', x=1638.58, y=5.62, z=962.15]]
	Chunk stats: MultiplayerChunkCache: 441
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (1637,4,953), Chunk: (at 5,0,9 in 102,59; contains blocks 1632,0,944 to 1647,255,959), Region: (3,1; contains chunks 96,32 to 127,63, blocks 1536,0,512 to 2047,255,1023)
	Level time: 2761 game time, 2761 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: 7 total; [rq['????π????'/127330, l='MpServer', x=1621.22, y=4.00, z=1040.75], rq['????π????'/127331, l='MpServer', x=1623.09, y=4.00, z=1040.06], rq['????π????'/127328, l='MpServer', x=1623.34, y=4.00, z=1041.66], ts['??????'/165094, l='MpServer', x=1605.63, y=4.57, z=897.72], rq['????π????'/127329, l='MpServer', x=1620.63, y=4.00, z=1039.53], bdi['bilakos96bill'/119313, l='MpServer', x=1638.58, y=5.62, z=962.15], ts['??????'/175509, l='MpServer', x=1594.50, y=4.00, z=945.50]]
	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: Mac OS X (x86_64) version 10.7.5
	Java Version: 1.6.0_51, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 176769184 bytes (168 MB) / 519565312 bytes (495 MB) up to 1065025536 bytes (1015 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 106 (5936 bytes; 0 MB) allocated, 2 (112 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: AMD Radeon HD 6750M OpenGL Engine GL version 2.1 ATI-7.32.12, ATI Technologies Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: ???????? (El)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 67 (3752 bytes; 0 MB) allocated, 19 (1064 bytes; 0 MB) used