Hopper: java.lang.ClassCastException: ans cannot be cast to ani

java.lang.ClassCastException: ans cannot be cast to ani
	at aij.a(SourceFile:200)

---- Minecraft Crash Report ----
// Shall we play a game?

Time: 11/3/13 4:04 PM
Description: Exception while updating neighbours

java.lang.ClassCastException: ans cannot be cast to ani
	at aij.a(SourceFile:200)
	at afn.e(SourceFile:480)
	at afn.d(SourceFile:463)
	at alm.m(SourceFile:136)
	at alm.a(SourceFile:179)
	at aoj.a(SourceFile:428)
	at afn.d(SourceFile:327)
	at ajd.h(SourceFile:117)
	at ajd.a(SourceFile:104)
	at mj.a(SourceFile:405)
	at mj.b(SourceFile:134)
	at net.minecraft.server.MinecraftServer.u(SourceFile:503)
	at net.minecraft.server.MinecraftServer.t(SourceFile:441)
	at bsk.t(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:358)
	at ky.run(SourceFile:617)


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

-- Head --
Stacktrace:
	at aij.a(SourceFile:200)

-- Block being updated --
Details:
	Source block type: ID #55 (tile.redstoneDust // alm)
	Block type: ID #54 (tile.chest // aij)
	Block data value: 5 / 0x5 / 0b0101
	Block location: World: (294,60,528), Chunk: (at 6,3,0 in 18,33; contains blocks 288,0,528 to 303,255,543), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
Stacktrace:
	at afn.e(SourceFile:480)
	at afn.d(SourceFile:463)
	at alm.m(SourceFile:136)
	at alm.a(SourceFile:179)
	at aoj.a(SourceFile:428)
	at afn.d(SourceFile:327)
	at ajd.h(SourceFile:117)
	at ajd.a(SourceFile:104)

-- Block being ticked --
Details:
	Block type: ID #8 (tile.water // ajd)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (295,60,525), Chunk: (at 7,3,13 in 18,32; contains blocks 288,0,512 to 303,255,527), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
Stacktrace:
	at mj.a(SourceFile:405)
	at mj.b(SourceFile:134)

-- Affected level --
Details:
	Level name: Lost in Bermuda Triangle
	All players: 0 total; []
	Chunk stats: ServerChunkCache: 626 Drop: 0
	Level seed: -4950017968147540182
	Level generator: ID 00 - default, ver 1. Features enabled: true
	Level generator options: 
	Level spawn location: World: (339,126,717), Chunk: (at 3,7,13 in 21,44; contains blocks 336,0,704 to 351,255,719), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
	Level time: 1007016 game time, 1011913 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 2297 (now: true), thunder time: 92129 (now: false)
	Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
	at net.minecraft.server.MinecraftServer.u(SourceFile:503)
	at net.minecraft.server.MinecraftServer.t(SourceFile:441)
	at bsk.t(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:358)
	at ky.run(SourceFile:617)

-- System Details --
Details:
	Minecraft Version: 1.7.2
	Operating System: Windows Vista (x86) version 6.0
	Java Version: 1.7.0_45, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 57060712 bytes (54 MB) / 140201984 bytes (133 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 192 (10752 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 517 (28952 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Player Count: 0 / 8; []
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.