I have played on this world with no problems for the first couple of times... note that the first time i could not open doors, chests, add or delete anything. This world has a big airport as you can see through the memory usage it takes. Now it crashes on downloading terrain and opens a crash report with ticking memory connection. Can anyone help me?

---- Minecraft Crash Report ----
// I bet Cylons wouldn't have this problem.

Time: 4/5/14 9:16 AM
Description: Ticking memory connection

java.lang.IllegalArgumentException: n must be positive
at java.util.Random.nextInt(Random.java:250)
at agx.a(SourceFile:183)
at agx.a(SourceFile:27)
at agr.a(SourceFile:364)
at apw.a(SourceFile:432)
at mr.a(SourceFile:165)
at aou.a(SourceFile:781)
at mr.c(SourceFile:100)
at mq.<init>(SourceFile:34)
at mp.a(SourceFile:220)
at mp.a(SourceFile:257)
at lm.a(SourceFile:155)
at lm.c(SourceFile:206)
at lm.a(SourceFile:100)
at nm.c(SourceFile:87)
at nm.a(SourceFile:52)
at eg.a(SourceFile:168)
at nb.c(SourceFile:134)
at net.minecraft.server.MinecraftServer.v(SourceFile:530)
at net.minecraft.server.MinecraftServer.u(SourceFile:443)
at btq.u(SourceFile:117)
at net.minecraft.server.MinecraftServer.run(SourceFile:359)
at lh.run(SourceFile:618)

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

– Head –
Stacktrace:
at java.util.Random.nextInt(Random.java:250)
at agx.a(SourceFile:183)
at agx.a(SourceFile:27)
at agr.a(SourceFile:364)
at apw.a(SourceFile:432)
at mr.a(SourceFile:165)
at aou.a(SourceFile:781)
at mr.c(SourceFile:100)
at mq.<init>(SourceFile:34)
at mp.a(SourceFile:220)
at mp.a(SourceFile:257)
at lm.a(SourceFile:155)
at lm.c(SourceFile:206)
at lm.a(SourceFile:100)
at nm.c(SourceFile:87)
at nm.a(SourceFile:52)
at eg.a(SourceFile:168)

– Ticking connection –
Details:
Connection: eg@3128482b
Stacktrace:
at nb.c(SourceFile:134)
at net.minecraft.server.MinecraftServer.v(SourceFile:530)
at net.minecraft.server.MinecraftServer.u(SourceFile:443)
at btq.u(SourceFile:117)
at net.minecraft.server.MinecraftServer.run(SourceFile:359)
at lh.run(SourceFile:618)

– System Details –
Details:
Minecraft Version: 1.7.5
Operating System: Mac OS X (x86_64) version 10.9.2
Java Version: 1.6.0_65, Apple Inc.
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
Memory: 2180306224 bytes (2079 MB) / 2282749952 bytes (2177 MB) up to 4277534720 bytes (4079 MB)
JVM Flags: 2 total; -Xmx4096M -Xms2048M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Player Count: 1 / 8; [mv['ChrispyT2'/899, l='Airport', x=-321.15, y=73.18, z=124.70]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.