Hopper: java.util.ConcurrentModificationException (SourceFile:63)

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-1960/

Crash:

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$KeyIterator.next(Unknown Source)
	at java.util.AbstractCollection.toArray(Unknown Source)
	at java.util.ArrayList.<init>(Unknown Source)
	at apy.k(SourceFile:63)
	at apy.a(SourceFile:207)

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

---- Minecraft Crash Report ----
// Daisy, daisy...

Time: 8/2/13 6:44 AM
Description: Exception while updating neighbours

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$KeyIterator.next(Unknown Source)
	at java.util.AbstractCollection.toArray(Unknown Source)
	at java.util.ArrayList.<init>(Unknown Source)
	at apy.k(SourceFile:63)
	at apy.a(SourceFile:207)
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:450)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:450)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:445)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:445)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:446)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:448)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:446)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)
	at abv.g(SourceFile:469)
	at ans.h_(SourceFile:238)
	at anm.c(SourceFile:187)
	at anm.a(SourceFile:198)
	at jr.a(SourceFile:404)
	at jr.b(SourceFile:130)
	at net.minecraft.server.MinecraftServer.t(SourceFile:462)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bkw.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at hh.run(SourceFile:582)


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

-- Head --
Stacktrace:
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$KeyIterator.next(Unknown Source)
	at java.util.AbstractCollection.toArray(Unknown Source)
	at java.util.ArrayList.<init>(Unknown Source)
	at apy.k(SourceFile:63)
	at apy.a(SourceFile:207)

-- Block being updated --
Details:
	Source block type: ID #55 (tile.redstoneDust // apy)
	Block type: ID #55 (tile.redstoneDust // apy)
	Block data value: 12 / 0xC / 0b1100
	Block location: World: (-266,13,-388), Chunk: (at 6,0,12 in -17,-25; contains blocks -272,0,-400 to -257,255,-385), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Stacktrace:
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:450)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)

-- Block being updated --
Details:
	Source block type: ID #55 (tile.redstoneDust // apy)
	Block type: ID #55 (tile.redstoneDust // apy)
	Block data value: 13 / 0xD / 0b1101
	Block location: World: (-266,13,-389), Chunk: (at 6,0,11 in -17,-25; contains blocks -272,0,-400 to -257,255,-385), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Stacktrace:
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:450)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)

-- Block being updated --
Details:
	Source block type: ID #55 (tile.redstoneDust // apy)
	Block type: ID #55 (tile.redstoneDust // apy)
	Block data value: 14 / 0xE / 0b1110
	Block location: World: (-266,13,-390), Chunk: (at 6,0,10 in -17,-25; contains blocks -272,0,-400 to -257,255,-385), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Stacktrace:
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:445)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)

-- Block being updated --
Details:
	Source block type: ID #55 (tile.redstoneDust // apy)
	Block type: ID #55 (tile.redstoneDust // apy)
	Block data value: 14 / 0xE / 0b1110
	Block location: World: (-265,13,-391), Chunk: (at 7,0,9 in -17,-25; contains blocks -272,0,-400 to -257,255,-385), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Stacktrace:
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:445)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)

-- Block being updated --
Details:
	Source block type: ID #55 (tile.redstoneDust // apy)
	Block type: ID #55 (tile.redstoneDust // apy)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (-264,13,-391), Chunk: (at 8,0,9 in -17,-25; contains blocks -272,0,-400 to -257,255,-385), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Stacktrace:
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:446)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)

-- Block being updated --
Details:
	Source block type: ID #55 (tile.redstoneDust // apy)
	Block type: ID #55 (tile.redstoneDust // apy)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (-264,13,-391), Chunk: (at 8,0,9 in -17,-25; contains blocks -272,0,-400 to -257,255,-385), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Stacktrace:
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:448)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)

-- Block being updated --
Details:
	Source block type: ID #55 (tile.redstoneDust // apy)
	Block type: ID #55 (tile.redstoneDust // apy)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (-264,13,-391), Chunk: (at 8,0,9 in -17,-25; contains blocks -272,0,-400 to -257,255,-385), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Stacktrace:
	at abv.g(SourceFile:469)
	at abv.f(SourceFile:446)
	at apy.k(SourceFile:67)
	at apy.a(SourceFile:207)

-- Block being updated --
Details:
	Source block type: ID #149 (tile.comparator // anm)
	Block type: ID #55 (tile.redstoneDust // apy)
	Block data value: 15 / 0xF / 0b1111
	Block location: World: (-266,13,-391), Chunk: (at 6,0,9 in -17,-25; contains blocks -272,0,-400 to -257,255,-385), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Stacktrace:
	at abv.g(SourceFile:469)
	at ans.h_(SourceFile:238)
	at anm.c(SourceFile:187)
	at anm.a(SourceFile:198)

-- Block being ticked --
Details:
	Block type: ID #149 (tile.comparator // anm)
	Block data value: 14 / 0xE / 0b1110
	Block location: World: (-266,13,-392), Chunk: (at 6,0,8 in -17,-25; contains blocks -272,0,-400 to -257,255,-385), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Stacktrace:
	at jr.a(SourceFile:404)
	at jr.b(SourceFile:130)

-- Affected level --
Details:
	Level name: cruise ship
	All players: 0 total; []
	Chunk stats: ServerChunkCache: 561 Drop: 0
	Level seed: 3163079738434915659
	Level generator: ID 01 - flat, ver 0. Features enabled: true
	Level generator options: 
	Level spawn location: World: (-336,4,-447), Chunk: (at 0,0,1 in -21,-28; contains blocks -336,0,-448 to -321,255,-433), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
	Level time: 2989280 game time, 925574 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 19392 (now: false), thunder time: 23181 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.t(SourceFile:462)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bkw.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at hh.run(SourceFile:582)

-- System Details --
Details:
	Minecraft Version: 1.6.2
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 17109816 bytes (16 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 78858 (4416048 bytes; 4 MB) allocated, 0 (0 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 13139 (735784 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.

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-1960/13951/