Google App Engine project raise exception after adding a servlet

Hi,

I am using IDEA 12 Ultimate  and Google App engine Java SDK 1.8.5 on Ubuntu 13.04 32-bit. When I create a simple App engine module and JPA 2 (data datanucleus) the application compile and run successfully and I can see the index.

But as soon as I add a Servlet (or any other Java class) to the project it can not compile and showes this stack trace:

Google AppEngine Enhancer: java.lang.RuntimeException: Unexpected exception
 at com.google.appengine.tools.enhancer.Enhancer.execute(Enhancer.java:76)
 at com.google.appengine.tools.enhancer.Enhance.<init>(Enhance.java:71)
 at com.google.appengine.tools.enhancer.Enhance.main(Enhance.java:51)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:606)
 at com.intellij.appengine.rt.EnhancerRunner.main(EnhancerRunner.java:36)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:606)
 at com.intellij.rt.execution.CommandLineWrapper.main(CommandLineWrapper.java:121)
Caused by: java.lang.reflect.InvocationTargetException
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:606)
 at com.google.appengine.tools.enhancer.Enhancer.execute(Enhancer.java:74)
 ... 12 more
Caused by: java.lang.NoSuchFieldError: NUCLEUS_CONTEXT_LOADER
 at org.datanucleus.NucleusContext.<clinit>(NucleusContext.java:75)
 at org.datanucleus.enhancer.DataNucleusEnhancer.<init>(DataNucleusEnhancer.java:160)
 at org.datanucleus.enhancer.DataNucleusEnhancer.main(DataNucleusEnhancer.java:1133)
 ... 17 more