Nullpointerexception keeps coming up any ideas?

Has anyone else seen this happening, it is occuring about 2 Day then it just disconnects everyone and needs to be restarted to clear it.

07:57:03 [SEVERE] java.lang.NullPointerException
07:57:03 [SEVERE]at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:63)
07:57:03 [SEVERE]at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:567)
07:57:03 [SEVERE]at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:459)
07:57:03 [SEVERE]at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
07:57:03 [SEVERE] Unexpected exception
java.lang.NullPointerException
at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:63)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:567)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:459)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)

 

Is this the entire error?

 

yes it is the entire error.

 

You have a plugin doing that to you. I'd start with plugins that change some of the internals of how CraftBukkit works, such as NoLagg or Spout.