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

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-203405/

Crash:

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 jr.d(SourceFile:116)
	at abw.e(SourceFile:289)
	at acl.<init>(SourceFile:32)
	at abw.a(SourceFile:2241)
	at rf.a(SourceFile:78)
	at rf.a(SourceFile:82)
	at qm.c(SourceFile:41)
	at pt.a(SourceFile:91)
	at og.bi(SourceFile:410)
	at of.c(SourceFile:1289)
	at og.c(SourceFile:292)
	at tm.c(SourceFile:24)
	at tw.c(SourceFile:141)
	at of.l_(SourceFile:1176)
	at og.l_(SourceFile:169)
	at tm.l_(SourceFile:29)
	at tw.l_(SourceFile:197)
	at abw.a(SourceFile:1349)
	at js.a(SourceFile:479)
	at abw.g(SourceFile:1327)

The following is the first clean report made public about this crash:

---- Minecraft Crash Report ----
// Don't be sad, have a hug! <3

Time: 21.09.13 20:47
Description: Ticking entity

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 jr.d(SourceFile:116)
	at abw.e(SourceFile:289)
	at acl.<init>(SourceFile:32)
	at abw.a(SourceFile:2241)
	at rf.a(SourceFile:78)
	at rf.a(SourceFile:82)
	at qm.c(SourceFile:41)
	at pt.a(SourceFile:91)
	at og.bi(SourceFile:410)
	at of.c(SourceFile:1289)
	at og.c(SourceFile:292)
	at tm.c(SourceFile:24)
	at tw.c(SourceFile:141)
	at of.l_(SourceFile:1176)
	at og.l_(SourceFile:169)
	at tm.l_(SourceFile:29)
	at tw.l_(SourceFile:197)
	at abw.a(SourceFile:1349)
	at js.a(SourceFile:479)
	at abw.g(SourceFile:1327)
	at abw.h(SourceFile:1234)
	at js.h(SourceFile:364)
	at net.minecraft.server.MinecraftServer.t(SourceFile:471)
	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 jr.d(SourceFile:116)
	at abw.e(SourceFile:289)
	at acl.<init>(SourceFile:32)
	at abw.a(SourceFile:2241)
	at rf.a(SourceFile:78)
	at rf.a(SourceFile:82)
	at qm.c(SourceFile:41)
	at pt.a(SourceFile:91)
	at og.bi(SourceFile:410)
	at of.c(SourceFile:1289)
	at og.c(SourceFile:292)
	at tm.c(SourceFile:24)
	at tw.c(SourceFile:141)
	at of.l_(SourceFile:1176)
	at og.l_(SourceFile:169)
	at tm.l_(SourceFile:29)
	at tw.l_(SourceFile:197)
	at abw.a(SourceFile:1349)
	at js.a(SourceFile:479)
	at abw.g(SourceFile:1327)

-- Entity being ticked --
Details:
	Entity Type: Zombie (tw)
	Entity ID: 10815
	Entity Name: Zombie
	Entity's Exact location: 507,50, 20,00, -311,50
	Entity's Block location: World: (507,20,-312), Chunk: (at 11,1,8 in 31,-20; contains blocks 496,0,-320 to 511,255,-305), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
	Entity's Momentum: 0,00, -0,08, 0,00
Stacktrace:
	at abw.h(SourceFile:1234)
	at js.h(SourceFile:364)

-- Affected level --
Details:
	Level name: Demo_World
	All players: 1 total; [jv['Player'/117, l='Demo_World', x=503,93, y=65,00, z=-422,09]]
	Chunk stats: ServerChunkCache: 1072 Drop: 0
	Level seed: -343522682
	Level generator: ID 00 - default, ver 1. Features enabled: true
	Level generator options: 
	Level spawn location: World: (216,64,-92), Chunk: (at 8,4,4 in 13,-6; contains blocks 208,0,-96 to 223,255,-81), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
	Level time: 8170 game time, 8170 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 120275 (now: false), thunder time: 23160 (now: false)
	Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
	at net.minecraft.server.MinecraftServer.t(SourceFile:471)
	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: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_05, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 83654232 bytes (79 MB) / 281935872 bytes (268 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 3337 (186872 bytes; 0 MB) allocated, 2787 (156072 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 7685 (430360 bytes; 0 MB) allocated, 6035 (337960 bytes; 0 MB) used
	Player Count: 1 / 8; [jv['Player'/117, l='Demo_World', x=503,93, y=65,00, z=-422,09]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-203405/12913325/