- Random Freeze (Read timed out)

This is a problem that is causing our server to FREEZE randomly.

CB: 1060
I've scanned the worlds through Chunkster.

Code:

2011-09-05 21:31:34 [SEVERE] java.lang.NullPointerException
2011-09-05 21:31:34 [SEVERE]     at net.minecraft.server.World.a(World.java:2058)
2011-09-05 21:31:34 [SEVERE]     at net.minecraft.server.SpawnerCreature.spawnEntities(SpawnerCreature.java:58)
2011-09-05 21:31:34 [SEVERE]     at net.minecraft.server.World.doTick(World.java:1715)
2011-09-05 21:31:34 [SEVERE]     at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:444)
2011-09-05 21:31:34 [SEVERE]     at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:363)
2011-09-05 21:31:34 [SEVERE]     at net.minecraft.server.ThreadServerApplication.run(SourceFile:422)
2011-09-05 21:31:34 [SEVERE] Unexpected exception
java.lang.NullPointerException
    at net.minecraft.server.World.a(World.java:2058)
    at net.minecraft.server.SpawnerCreature.spawnEntities(SpawnerCreature.java:58)
    at net.minecraft.server.World.doTick(World.java:1715)
    at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:444)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:363)
    at net.minecraft.server.ThreadServerApplication.run(SourceFile:422)

Help would have been greatly appreciated.
I've got serveral thoughts, but I'd like to know what you think of this error.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Looks like this has something to do with a plugin that is spawning mobs or limiting the spawning of Mobs on your server. Check plugins that perform these actions for updates. Also turning off mob spawning from the server.prop may also be useful to see if you get different results.