Weird crash when moving around

I was moving around in my world (created in 1.5). Suddenly, the game crashes with an IllegalArgumentException in aeg.class (by decompiling aeg.class and looking at the code seems to be related to world generation). Reloading the game lets me back in normally, but after playing for some time the same crash occurs.

I have edited my world using MCEdit to copy/paste blocks.

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

Time: 21.9.2013 15:01
Description: Ticking memory connection

java.lang.IllegalArgumentException: n must be positive
	at java.util.Random.nextInt(Unknown Source)
	at aeg.a(SourceFile:183)
	at aeg.a(SourceFile:27)
	at aea.a(SourceFile:354)
	at aej.a(SourceFile:42)
	at agn.a(SourceFile:428)
	at km.a(SourceFile:156)
	at afk.a(SourceFile:778)
	at km.c(SourceFile:93)
	at kl.<init>(SourceFile:28)
	at kk.a(SourceFile:209)
	at kk.d(SourceFile:343)
	at jh.d(SourceFile:211)
	at kv.a(SourceFile:270)
	at gn.a(SourceFile:136)
	at eb.b(SourceFile:63)
	at kv.e(SourceFile:64)
	at ky.b(SourceFile:37)
	at bow.b(SourceFile:83)
	at net.minecraft.server.MinecraftServer.u(SourceFile:487)
	at net.minecraft.server.MinecraftServer.t(SourceFile:404)
	at bot.t(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:338)
	at jc.run(SourceFile:581)


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

-- Head --
Stacktrace:
	at java.util.Random.nextInt(Unknown Source)
	at aeg.a(SourceFile:183)
	at aeg.a(SourceFile:27)
	at aea.a(SourceFile:354)
	at aej.a(SourceFile:42)
	at agn.a(SourceFile:428)
	at km.a(SourceFile:156)
	at afk.a(SourceFile:778)
	at km.c(SourceFile:93)
	at kl.<init>(SourceFile:28)
	at kk.a(SourceFile:209)
	at kk.d(SourceFile:343)
	at jh.d(SourceFile:211)
	at kv.a(SourceFile:270)
	at gn.a(SourceFile:136)
	at eb.b(SourceFile:63)
	at kv.e(SourceFile:64)

-- Ticking connection --
Details:
	Connection: kv@7f832772
Stacktrace:
	at ky.b(SourceFile:37)
	at bow.b(SourceFile:83)
	at net.minecraft.server.MinecraftServer.u(SourceFile:487)
	at net.minecraft.server.MinecraftServer.t(SourceFile:404)
	at bot.t(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:338)
	at jc.run(SourceFile:581)

-- System Details --
Details:
	Minecraft Version: 13w38c
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_10, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 272648144 bytes (260 MB) / 574291968 bytes (547 MB) up to 3817799680 bytes (3640 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx4G
	AABB Pool Size: 2088 (116928 bytes; 0 MB) allocated, 2037 (114072 bytes; 0 MB) used
	IntCache: cache: 1, tcache: 1, allocated: 12, tallocated: 94
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 299 (16744 bytes; 0 MB) allocated, 270 (15120 bytes; 0 MB) used
	Player Count: 1 / 8; [kq['Pietu1998'/252422, l='New World', x=32,01, y=38,00, z=71,49]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.