Hopper: java.lang.ClassCastException: aqu cannot be cast to amy

java.lang.ClassCastException: aqu cannot be cast to amy
	at amz.<init>(SourceFile:33)
	at amy.a(SourceFile:372)
	at amy.a(SourceFile:334)
	at adr.a(SourceFile:395)
	at abw.f(SourceFile:306)
	at ait.a(SourceFile:417)
	at ait.a(SourceFile:546)
	at agi.a(SourceFile:442)
	at aiv.a(SourceFile:37)
	at ain.a(SourceFile:87)
	at aet.a(SourceFile:425)
	at jr.a(SourceFile:168)
	at adr.a(SourceFile:732)
	at jr.c(SourceFile:105)
	at jq.<init>(SourceFile:29)
	at jp.a(SourceFile:208)
	at jp.d(SourceFile:337)
	at hn.d(SourceFile:197)
	at ka.a(SourceFile:267)
	at eu.a(SourceFile:136)
	at cn.b(SourceFile:64)
	at ka.e(SourceFile:60)

---- Minecraft Crash Report ----
// There are four lights!

Time: 9/19/13 5:40 PM
Description: Ticking memory connection

java.lang.ClassCastException: aqu cannot be cast to amy
	at amz.<init>(SourceFile:33)
	at amy.a(SourceFile:372)
	at amy.a(SourceFile:334)
	at adr.a(SourceFile:395)
	at abw.f(SourceFile:306)
	at ait.a(SourceFile:417)
	at ait.a(SourceFile:546)
	at agi.a(SourceFile:442)
	at aiv.a(SourceFile:37)
	at ain.a(SourceFile:87)
	at aet.a(SourceFile:425)
	at jr.a(SourceFile:168)
	at adr.a(SourceFile:732)
	at jr.c(SourceFile:105)
	at jq.<init>(SourceFile:29)
	at jp.a(SourceFile:208)
	at jp.d(SourceFile:337)
	at hn.d(SourceFile:197)
	at ka.a(SourceFile:267)
	at eu.a(SourceFile:136)
	at cn.b(SourceFile:64)
	at ka.e(SourceFile:60)
	at kd.b(SourceFile:37)
	at blc.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:489)
	at net.minecraft.server.MinecraftServer.s(SourceFile:406)
	at bkz.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:340)
	at hi.run(SourceFile:583)


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

-- Head --
Stacktrace:
	at amz.<init>(SourceFile:33)
	at amy.a(SourceFile:372)
	at amy.a(SourceFile:334)
	at adr.a(SourceFile:395)
	at abw.f(SourceFile:306)
	at ait.a(SourceFile:417)
	at ait.a(SourceFile:546)
	at agi.a(SourceFile:442)
	at aiv.a(SourceFile:37)
	at ain.a(SourceFile:87)
	at aet.a(SourceFile:425)
	at jr.a(SourceFile:168)
	at adr.a(SourceFile:732)
	at jr.c(SourceFile:105)
	at jq.<init>(SourceFile:29)
	at jp.a(SourceFile:208)
	at jp.d(SourceFile:337)
	at hn.d(SourceFile:197)
	at ka.a(SourceFile:267)
	at eu.a(SourceFile:136)
	at cn.b(SourceFile:64)
	at ka.e(SourceFile:60)

-- Ticking connection --
Details:
	Connection: ka@6982bec3
Stacktrace:
	at kd.b(SourceFile:37)
	at blc.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:489)
	at net.minecraft.server.MinecraftServer.s(SourceFile:406)
	at bkz.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:340)
	at hi.run(SourceFile:583)

-- System Details --
Details:
	Minecraft Version: 1.6.4
	Operating System: Mac OS X (x86_64) version 10.6.8
	Java Version: 1.6.0_37, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 59359496 bytes (56 MB) / 261029888 bytes (248 MB) up to 1069416448 bytes (1019 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 7484 (419104 bytes; 0 MB) allocated, 6671 (373576 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 7021 (393176 bytes; 0 MB) allocated, 6607 (369992 bytes; 0 MB) used
	Player Count: 1 / 8; [jv['LukeB245'/318, l='New World', x=1209.38, y=94.03, z=387.40]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.