In case someone else runs into this error, I narrowed the problem down to our using Xerces as the XML parser for Jdom. I removed xerces.jar and xml-apis.jar from our build process and the problem went away. In our JDom configuration code, I needed to use the org.jdom.adapters.JAXPDOMAdapter rather than the org.jdom.adapters.XercesDomAdapter. I'm not sure if JBoss doesn't like a particular version of Xerces or all versions, but switching to the JAXP parser (which is included in the JDK libraries) made this problem go away. I can now run the Seam examples using the embedded EJB3 library in an embedded version of Tomcat within our Java server application. Hope this helps, Guy View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4007467#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...