sourceID on JOnAS

Hello,

I've dowloaded sourceID.java from http://www.sourceId.org/. The sample 
sourceid-sso.war enables to authenticate a user with an IDP Liberty.
sourceid-sso.war works well on Tomcat alone  but when I install JOnAS, 
the sample doesn't work and I have the following error :

An error occured. Replace this page (or the pointer in sourceid-sso.xml) 
with a "real" error page.

      === Throwable (or Exception) information ===
throwable class name: org.exolab.castor.xml.MarshalException
toString(): instantiation error for class: 
org.sourceid.sso.xml.samlp.ResponseTypeDescriptor; 
java.lang.ClassCastException
getMessage(): instantiation error for class: 
org.sourceid.sso.xml.samlp.ResponseTypeDescriptor; 
java.lang.ClassCastException
Stack Trace: instantiation error for class: 
org.sourceid.sso.xml.samlp.ResponseTypeDescriptor; 
java.lang.ClassCastException
  at 
org.exolab.castor.xml.Marshaller.getClassDescriptor(Marshaller.java:1110)
  at org.exolab.castor.xml.Marshaller.marshal(Marshaller.java:661)

Thanks.

Anne