Cache problem?

1. Im using Windows 7
2. My java version is 1.6.0_17-bo4
3. Im not using any wrappers
4. Im using build 766
5. Im getting this MASSIVE error spam

Code:

12:55:52 [INFO] Chunk (18, -4) stored at  (18, -3)
12:55:52 [INFO] net.minecraft.server.Chunk
12:55:52 [SEVERE] java.lang.Throwable
12:55:52 [SEVERE]      at net.minecraft.server.ChunkProviderServer.getOrCreateC
hunk(ChunkProviderServer.java:120)
12:55:52 [SEVERE]      at net.minecraft.server.World.getChunkAt(World.java:215)

12:55:52 [SEVERE]      at net.minecraft.server.World.b(World.java:1741)
12:55:52 [SEVERE]      at net.minecraft.server.World.getEntities(World.java:840
)
12:55:52 [SEVERE]      at net.minecraft.server.Entity.move(Entity.java:391)
12:55:52 [SEVERE]      at net.minecraft.server.EntityLiving.a(EntityLiving.java
:570)
12:55:52 [SEVERE]      at net.minecraft.server.EntityLiving.u(EntityLiving.java
:676)
12:55:52 [SEVERE]      at net.minecraft.server.EntityMonster.u(EntityMonster.ja
va:30)
12:55:52 [SEVERE]      at net.minecraft.server.EntityZombie.u(EntityZombie.java
:34)
12:55:52 [SEVERE]      at net.minecraft.server.EntityLiving.p_(EntityLiving.jav
a:231)
12:55:52 [SEVERE]      at net.minecraft.server.EntityMonster.p_(EntityMonster.j
ava:34)
12:55:52 [SEVERE]      at net.minecraft.server.World.entityJoinedWorld(World.ja
va:1009)
12:55:52 [SEVERE]      at net.minecraft.server.WorldServer.entityJoinedWorld(Wo
rldServer.java:53)
12:55:52 [SEVERE]      at net.minecraft.server.World.playerJoinedWorld(World.ja
va:991)
12:55:52 [SEVERE]      at net.minecraft.server.World.cleanUp(World.java:968)
12:55:52 [SEVERE]      at net.minecraft.server.MinecraftServer.h(MinecraftServe
r.java:369)
12:55:52 [SEVERE]      at net.minecraft.server.MinecraftServer.run(MinecraftSer
ver.java:287)
12:55:52 [SEVERE]      at net.minecraft.server.ThreadServerApplication.run(Sour
ceFile:394)

6. Iv tried restarting my PC, Breaking and placing blocks, redownloading some plugins.
7. Please help

 

You will need to play with a tool called Chunkster.