Java exception in Advanced Call Web Service Plug-in

I am trying to use this plugin but I am getting the folowing error:

javax.xml.ws.WebServiceException: java.lang.ClassCastException: com.sun.xml.ws.message.saaj.SAAJHeader cannot be cast to com.sun.xml.ws.security.opt.impl.outgoing.SecurityHeader

Any idea why this would be?

Thanks for any insight.