Hopper: java.lang.ArrayIndexOutOfBoundsException: -1

java.lang.ArrayIndexOutOfBoundsException: -1
	at java.util.ArrayList.fastRemove(ArrayList.java:528)
	at java.util.ArrayList.remove(ArrayList.java:511)
	at jq.b(SourceFile:52)
	at jp.c(SourceFile:302)
	at hn.e(SourceFile:211)
	at ka.a(SourceFile:398)
	at cn.b(SourceFile:72)
	at ka.e(SourceFile:60)

---- Minecraft Crash Report ----
// Don't be sad. I'll do better next time, I promise!

Time: 10/2/13 7:07 PM
Description: Ticking memory connection

java.lang.ArrayIndexOutOfBoundsException: -1
	at java.util.ArrayList.fastRemove(ArrayList.java:528)
	at java.util.ArrayList.remove(ArrayList.java:511)
	at jq.b(SourceFile:52)
	at jp.c(SourceFile:302)
	at hn.e(SourceFile:211)
	at ka.a(SourceFile:398)
	at cn.b(SourceFile:72)
	at ka.e(SourceFile:60)
	at kd.b(SourceFile:37)
	at blc.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:489)
	at net.minecraft.server.MinecraftServer.s(SourceFile:406)
	at bkz.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:340)
	at hi.run(SourceFile:583)


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

-- Head --
Stacktrace:
	at java.util.ArrayList.fastRemove(ArrayList.java:528)
	at java.util.ArrayList.remove(ArrayList.java:511)
	at jq.b(SourceFile:52)
	at jp.c(SourceFile:302)
	at hn.e(SourceFile:211)
	at ka.a(SourceFile:398)
	at cn.b(SourceFile:72)
	at ka.e(SourceFile:60)

-- Ticking connection --
Details:
	Connection: ka@2f669674
Stacktrace:
	at kd.b(SourceFile:37)
	at blc.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:489)
	at net.minecraft.server.MinecraftServer.s(SourceFile:406)
	at bkz.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:340)
	at hi.run(SourceFile:583)

-- System Details --
Details:
	Minecraft Version: 1.6.4
	Operating System: Mac OS X (x86_64) version 10.8.4
	Java Version: 1.7.0_40, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 148594456 bytes (141 MB) / 301989888 bytes (288 MB) up to 954728448 bytes (910 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 4349 (243544 bytes; 0 MB) allocated, 4014 (224784 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 5720 (320320 bytes; 0 MB) allocated, 5276 (295456 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.