Hopper: java.lang.OutOfMemoryError: Java heap space

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-294476/

Crash:

java.lang.OutOfMemoryError: Java heap space
java.lang.OutOfMemoryError: Java heap space

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

---- Minecraft Crash Report ----
// Hey, that tickles! Hehehe!

Time: 11-10-13 22:08
Description: Exception in server tick loop

java.lang.OutOfMemoryError: Java heap space
	at java.util.TreeMap.put(Unknown Source)
	at java.util.TreeSet.add(Unknown Source)
	at jp.a(SourceFile:335)
	at jp.a(SourceFile:306)
	at aol.a(SourceFile:24)
	at adm.a(SourceFile:395)
	at abr.f(SourceFile:307)
	at afl.a(SourceFile:63)
	at acp.a(SourceFile:227)
	at acp.b(SourceFile:242)
	at acp.a(SourceFile:68)
	at acp.a(SourceFile:27)
	at acl.a(SourceFile:217)
	at acs.a(SourceFile:21)
	at aej.a(SourceFile:155)
	at jo.a(SourceFile:168)
	at adm.a(SourceFile:732)
	at jo.c(SourceFile:105)
	at net.minecraft.server.MinecraftServer.f(SourceFile:229)
	at bko.a(SourceFile:90)
	at bko.d(SourceFile:106)
	at net.minecraft.server.MinecraftServer.run(SourceFile:314)
	at hf.run(SourceFile:582)


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

-- System Details --
Details:
	Minecraft Version: 1.6.1
	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: 9753384 bytes (9 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: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 0 (0 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-294476/16918748/