Server crashing when a certain user joins

[shanefleming]

Title: Server crashing when a certain user joins

Version: 3.1.3

OS: Windows Server 2008

Java Version: newest

Description of Problem:

When a cetain user joins the

Error Messages:

Error Log:

Caused by: java.lang.ClassNotFoundException: org.bukkit.entity.Wither

        at java.net.URLClassLoader$1.run(Unknown Source)

        at java.net.URLClassLoader$1.run(Unknown Source)

        at java.security.AccessController.doPrivileged(Native Method)

        at java.net.URLClassLoader.findClass(Unknown Source)

        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.

java:41)

        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.

java:29)

        at java.lang.ClassLoader.loadClass(Unknown Source)

        at java.lang.ClassLoader.loadClass(Unknown Source)

        ... 19 more

2013-02-06 00:39:54 [sEVERE] Could not pass event EntityExplodeEvent to WorldGua

rd

org.bukkit.event.EventException

        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.ja

va:304)

        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.jav

a:62)

        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.j

ava:482)

        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.j

ava:467)

        at net.minecraft.server.EntityEnderDragon.a(EntityEnderDragon.java:493)

        at net.minecraft.server.EntityEnderDragon.e(EntityEnderDragon.java:330)

        at net.minecraft.server.EntityLiving.F_(EntityLiving.java:455)

        at net.minecraft.server.World.entityJoinedWorld(World.java:1285)

        at net.minecraft.server.WorldServer.entityJoinedWorld(WorldServer.java:1

04)

        at net.minecraft.server.World.playerJoinedWorld(World.java:1267)

        at net.minecraft.server.World.tickEntities(World.java:1163)

        at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:559)

        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:457)

        at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)

Caused by: java.lang.NoClassDefFoundError: org/bukkit/entity/Wither

        at com.sk89q.worldguard.bukkit.WorldGuardEntityListener.onEntityExplode(

WorldGuardEntityListener.java:551)

        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

        at java.lang.reflect.Method.invoke(Unknown Source)

        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.ja

va:302)

        ... 13 more