Crash on loading (Ticking block entity java.util.ConcurrentModificationException)

At least I got a hug

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

Time: 7/23/14 12:08 PM
Description: Ticking block entity

java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
	at java.util.ArrayList$Itr.next(Unknown Source)
	at apv.a(SourceFile:1732)
	at bdy.e(SourceFile:690)
	at apv.s(SourceFile:1709)
	at bbi.a(SourceFile:222)
	at bbi.m(SourceFile:214)
	at bbi.c(SourceFile:246)
	at apv.i(SourceFile:1315)
	at brk.r(SourceFile:1830)
	at brk.ar(SourceFile:875)
	at brk.a(SourceFile:310)
	at net.minecraft.client.main.Main.main(SourceFile:120)


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 apv.a(SourceFile:1732)
	at bdy.e(SourceFile:690)
	at apv.s(SourceFile:1709)
	at bbi.a(SourceFile:222)
	at bbi.m(SourceFile:214)
	at bbi.c(SourceFile:246)

-- Block entity being ticked --
Details:
	Name: Chest // bbi
	Block type: ID #54 (tile.chest // ath)
	Block data value: 5 / 0x5 / 0b0101
	Block location: World: (19,67,87), Chunk: (at 3,4,7 in 1,5; contains blocks 16,0,80 to 31,255,95), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Actual block type: ID #54 (tile.chest // ath)
	Actual block data value: 5 / 0x5 / 0b0101
Stacktrace:
	at apv.i(SourceFile:1315)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [cgv['Johns_World3'/460, l='MpServer', x=-6.29, y=36.00, z=80.36]]
	Chunk stats: MultiplayerChunkCache: 529, 529
	Level seed: 0
	Level generator: ID 03 - amplified, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: -60.00,64.00,248.00 - World: (-60,64,248), Chunk: (at 4,4,8 in -4,15; contains blocks -64,0,240 to -49,255,255), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
	Level time: 36914839 game time, 40608903 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
	
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at ccu.a(SourceFile:308)
	at brk.b(SourceFile:2262)
	at brk.a(SourceFile:319)
	at net.minecraft.client.main.Main.main(SourceFile:120)

-- System Details --
Details:
	Minecraft Version: 14w30b
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_51, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 604805568 bytes (576 MB) / 1037565952 bytes (989 MB) up to 1908932608 bytes (1820 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx2G
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Launched Version: 14w30b
	LWJGL: 2.9.1
	OpenGL: GeForce GT 545/PCIe/SSE2 GL version 4.4.0, NVIDIA Corporation
	GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

	Using VBOs: No
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: []
	Current Language: English (US)
	Profiler Position: N/A (disabled)

(Sorry had to delete dome things due to word limit)