Hi,
the code that sets the SOAPAction header relies on the metadata you see having that info; http://anonsvn.jboss.org/repos/jbossws/stack/native/tags/jbossws-native-3.2.1.GA/modules/core/src/main/java/org/jboss/ws/core/jaxws/binding/SOAPBindingJAXWS.java .
Can you double check you're not overwriting the soapAction thorugh the message context? Also, addressing might play a role in this.
Generally speaking, also consider trying a more recent jbossws version.