If a deployment uses JAXP such as Xerces XML parsing inside of the application and requires a different version of Xerces or JAXP implementation and the deployment also uses Web Services such to call a WS client, then the WS call will fail because JBossWS will get a ClassCastException because JBossWS is running in the context of the deployment and tries to use the JAXP implementation in the deployment instead of the implementation in JBoss which it should.

We need to look at fixing JBossWS to use the classloader where the JBossWS classes are located instead of the classloader of the deployment when creating factories.