Well, the game will just crash for no reason in an area, and the crash report is this:

---- Minecraft Crash Report ----
// Surprise! Haha. Well, this is awkward.

Time: 8/24/14 2:04 PM
Description: Ticking memory connection

java.lang.IllegalArgumentException: n must be positive
at java.util.Random.nextInt(Unknown Source)
at aia.a(SourceFile:122)
at aia.a(SourceFile:27)
at ahu.a(SourceFile:364)
at aif.a(SourceFile:138)
at aqz.a(SourceFile:432)
at ms.a(SourceFile:166)
at apx.a(SourceFile:778)
at ms.c(SourceFile:101)
at mr.<init>(SourceFile:34)
at mq.a(SourceFile:220)
at mq.d(SourceFile:354)
at oi.d(SourceFile:235)
at nh.a(SourceFile:282)
at jd.a(SourceFile:137)
at je.a(SourceFile:63)
at ej.a(SourceFile:174)
at nc.c(SourceFile:134)
at net.minecraft.server.MinecraftServer.v(SourceFile:540)
at net.minecraft.server.MinecraftServer.u(SourceFile:453)
at bsx.u(SourceFile:117)
at net.minecraft.server.MinecraftServer.run(SourceFile:369)
at lj.run(SourceFile:628)

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 aia.a(SourceFile:122)
at aia.a(SourceFile:27)
at ahu.a(SourceFile:364)
at aif.a(SourceFile:138)
at aqz.a(SourceFile:432)
at ms.a(SourceFile:166)
at apx.a(SourceFile:778)
at ms.c(SourceFile:101)
at mr.<init>(SourceFile:34)
at mq.a(SourceFile:220)
at mq.d(SourceFile:354)
at oi.d(SourceFile:235)
at nh.a(SourceFile:282)
at jd.a(SourceFile:137)
at je.a(SourceFile:63)
at ej.a(SourceFile:174)

– Ticking connection –
Details:
Connection: ej@483f635e
Stacktrace:
at nc.c(SourceFile:134)
at net.minecraft.server.MinecraftServer.v(SourceFile:540)
at net.minecraft.server.MinecraftServer.u(SourceFile:453)
at bsx.u(SourceFile:117)
at net.minecraft.server.MinecraftServer.run(SourceFile:369)
at lj.run(SourceFile:628)

– System Details –
Details:
Minecraft Version: 1.7.10
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.7.0_07, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 1370032624 bytes (1306 MB) / 1543503872 bytes (1472 MB) up to 1543503872 bytes (1472 MB)
JVM Flags: 3 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1536M -Xms1536M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Player Count: 1 / 8; [mw['haloman30'/28, l='Halo', x=639.84, y=243.00, z=1287.24]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.