Fehler bei Mods laden

A problem occurred running the Server launcher.java.lang.reflect.InvocationTargetException
    	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 cpw.mods.fml.relauncher.ServerLaunchWrapper.run(ServerLaunchWrapper.java:43)
    	at cpw.mods.fml.relauncher.ServerLaunchWrapper.main(ServerLaunchWrapper.java:12)
Caused by: java.lang.NoClassDefFoundError: org/apache/logging/log4j/Level
    	at net.minecraft.launchwrapper.Launch.launch(Launch.java:94)
    	at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
    	... 6 more
Caused by: java.lang.ClassNotFoundException: org.apache.logging.log4j.Level
    	at java.net.URLClassLoader$1.run(Unknown Source)
    	at java.net.URLClassLoader$1.run(Unknown Source)
    	at java.security.AccessController.doPrivileged(Native Method)
    	at java.net.URLClassLoader.findClass(Unknown Source)
    	at java.lang.ClassLoader.loadClass(Unknown Source)
    	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    	at java.lang.ClassLoader.loadClass(Unknown Source)
    	... 8 more