Orebfuscator Error

2012-08-19 20:02:28 [SEVERE] Could not load 'plugins/Orebfuscator.jar' in folder 'plugins'

org.bukkit.plugin.InvalidPluginException: java.lang.NoClassDefFoundError: net/minecraft/serverhook/NetServerHandlerProxy

    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:153)

    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:305)

    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:230)

    at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:222)

    at org.bukkit.craftbukkit.CraftServer.<init>(CraftServer.java:198)

    at net.minecraft.server.ServerConfigurationManagerAbstract.<init>(ServerConfigurationManagerAbstract.java:50)

    at net.minecraft.server.ServerConfigurationManager.<init>(SourceFile:11)

    at net.minecraft.server.DedicatedServer.init(DedicatedServer.java:105)

    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:378)

    at net.minecraft.server.ThreadServerApplication.run(SourceFile:539)

Caused by: java.lang.NoClassDefFoundError: net/minecraft/serverhook/NetServerHandlerProxy

    at java.lang.ClassLoader.defineClass1(Native Method)

    at java.lang.ClassLoader.defineClass(ClassLoader.java:791)

    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)

    at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)

    at java.net.URLClassLoader.access$100(URLClassLoader.java:71)

    at java.net.URLClassLoader$1.run(URLClassLoader.java:361)

    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)

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

    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)

    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:44)

    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)

    at java.lang.ClassLoader.loadClass(ClassLoader.java:423)

    at java.lang.ClassLoader.loadClass(ClassLoader.java:356)

    at com.lishid.orebfuscator.Orebfuscator.<init>(Orebfuscator.java:55)

    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)

    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

    at java.lang.reflect.Constructor.newInstance(Constructor.java:525)

    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:149)

    ... 9 more

Caused by: java.lang.ClassNotFoundException: net.minecraft.serverhook.NetServerHandlerProxy

    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:34)

    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)

    at java.lang.ClassLoader.loadClass(ClassLoader.java:423)

    at java.lang.ClassLoader.loadClass(ClassLoader.java:356)

    ... 28 more