Hopper: java.util.ConcurrentModificationException

java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
	at java.util.ArrayList$Itr.next(Unknown Source)
	at java.util.Collections$UnmodifiableCollection$1.next(Unknown Source)
	at bgg.a(SourceFile:67)
	at bgb.c(SourceFile:105)

---- Minecraft Crash Report ----
// Uh... Did I do that?

Time: 10/25/13 8:47 PM
Description: Ticking screen

java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
	at java.util.ArrayList$Itr.next(Unknown Source)
	at java.util.Collections$UnmodifiableCollection$1.next(Unknown Source)
	at bgg.a(SourceFile:67)
	at bgb.c(SourceFile:105)
	at azd.o(SourceFile:1318)
	at azd.ad(SourceFile:753)
	at azd.e(SourceFile:704)
	at net.minecraft.client.main.Main.main(SourceFile:103)


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 java.util.Collections$UnmodifiableCollection$1.next(Unknown Source)
	at bgg.a(SourceFile:67)
	at bgb.c(SourceFile:105)

-- Affected screen --
Details:
	Screen name: bgb
Stacktrace:
	at azd.o(SourceFile:1318)
	at azd.ad(SourceFile:753)
	at azd.e(SourceFile:704)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 1.7.2
	Operating System: Windows 8 (x86) version 6.2
	Java Version: 1.7.0_17, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 198600392 bytes (189 MB) / 429559808 bytes (409 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 3747 (209832 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Launched Version: 1.7.2
	LWJGL: 2.9.0
	OpenGL: AMD Radeon HD 6290 Graphics GL version 4.2.11764 Compatibility Profile Context, ATI Technologies Inc.
	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)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null
	Anisotropic Filtering: Off (1)