I have similar problem as described in http://tech.forums.softwareag.com/techjforum/posts/list/58467.page.
I have CAF application that calls WebServices by client generated by wsimport from WSDL files. WEB-INF/lib contains 30+ jars but some of them conflicts with jars bundled with MWS: stax-1.2.0.jar
stax-API-1.0.1.jar
wstx-asl-3.2.7.jar
and resulting in following error:

After removing these jars from WEB-INF/lib there is another problem:

wsimport generates classes with following annotations:

@XmlType(name = "Document", namespace = "http://schemas.company.pl/pemg/213", propOrder = {
"createEvtReq"
})
public class Document { }

@XmlType(name = "Document", namespace = "http://schemas.company.pl/pemg/214", propOrder = {
"createEvtResp"
})
public class Document { }

and soap client with namespace http://soap.company.pl/pemg/301

@WebServiceClient(name = "Event", targetNamespace = "http://soap.company.pl/pemg/301", wsdlLocation = "/wsdl/Event.wsdl")
public class Event extends Service { }

In runtime Document classes have got namespace from soap client instead of their own namespace defined in annotation. This creates a name conflict, because there are multiple XML types with the same name (Document) and namespace (http://soap.company.pl/pemg/301)
This can be some bug in the implementation of JAX-WS/JAXB delivered with MWS or some mismatch with versions, but I’m out of ideas how to solve this.