---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 20/06/14 3:32 PM
Description: Executing command block

java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
	at java.util.ArrayList$Itr.next(Unknown Source)
	at alu.a(SourceFile:2273)
	at af.b(SourceFile:326)
	at ab.a(SourceFile:47)
	at alg.a(SourceFile:92)
	at apb.c(SourceFile:56)
	at ou.a(SourceFile:466)
	at ou.c(SourceFile:176)
	at net.minecraft.server.MinecraftServer.w(SourceFile:570)
	at net.minecraft.server.MinecraftServer.v(SourceFile:506)
	at coe.v(SourceFile:132)
	at net.minecraft.server.MinecraftServer.run(SourceFile:422)
	at java.lang.Thread.run(Unknown Source)


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

-- Head --
Stacktrace:
	at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
	at java.util.ArrayList$Itr.next(Unknown Source)
	at alu.a(SourceFile:2273)
	at af.b(SourceFile:326)
	at ab.a(SourceFile:47)

-- Command to be executed --
Details:
	Command: /execute @e[type=Bat] ~ ~ ~ /clone -298 56 -537 -298 61 -537 ~ ~-8 ~ masked
	Name: @
Stacktrace:
	at alg.a(SourceFile:92)
	at apb.c(SourceFile:56)

-- Block being ticked --
Details:
	Block type: ID #137 (tile.commandBlock // apb)
	Block data value: 1 / 0x1 / 0b0001
	Block location: World: (-297,56,-537), Chunk: (at 7,3,7 in -19,-34; contains blocks -304,0,-544 to -289,255,-529), Region: (-1,-2; contains chunks -32,-64 to -1,-33, blocks -512,0,-1024 to -1,255,-513)
Stacktrace:
	at ou.a(SourceFile:466)
	at ou.c(SourceFile:176)

-- Affected level --
Details:
	Level name: 14w25a bug test
	All players: 0 total; []
	Chunk stats: ServerChunkCache: 1221 Drop: 0
	Level seed: 4075514539998324942
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 3;minecraft:bedrock,3*minecraft:stone,52*minecraft:sandstone;2;
	Level spawn location: 0.00,4.00,-403.00 - World: (0,4,-403), Chunk: (at 0,0,13 in 0,-26; contains blocks 0,0,-416 to 15,255,-401), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
	Level time: 27511 game time, 31058 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 11908 (now: true), thunder time: 33452 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.w(SourceFile:570)
	at net.minecraft.server.MinecraftServer.v(SourceFile:506)
	at coe.v(SourceFile:132)
	at net.minecraft.server.MinecraftServer.run(SourceFile:422)
	at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
	Minecraft Version: 14w25b
	Operating System: Windows 8.1 (amd64) version 6.3
	Java Version: 1.8.0, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 3933400760 bytes (3751 MB) / 4200071168 bytes (4005 MB) up to 4772593664 bytes (4551 MB)
	JVM Flags: 3 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx5120m -Xms2560m
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Profiler Position: N/A (disabled)
	Player Count: 0 / 8; []
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.