Hello there! From what I've searched so far, this error happens when I have a sun RI SAAJ in my classloader. I've searched my entire harddisk (literally) for a reference to anothar SAAJ implementation that's not jboss-saaj.jar. And could not find. I've also used some operations on the classloader mbean (output bellow) to find who was loading the other instance. And yet, nothing was found. The error happens when my WebServiceProvider using ServiceMode=Mode.MESSAGE is invoked. Anything else should I be looking for? Regards | getPackage | org.jboss.mx.loading.UnifiedClassLoader3@6f9b8e{ url=null ,addedOrder=2}, org.jboss.mx.loading.UnifiedClassLoader3@1b70f9e{ url=file:/java/servers/jboss-messaging/server/messaging/deploy/jboss-messaging.sar/ ,addedOrder=12}, | org.jboss.mx.loading.UnifiedClassLoader3@1f6d2e3{ url=file:/java/servers/jboss-messaging/server/messaging/deploy/jbossws.sar/ ,addedOrder=13} | | | displayClassInfo | javax.xml.soap.SOAPMessage Information | Repository cache version: | javax.xml.soap.SOAPMessage(8f6d64).ClassLoader=null | ++++Null CodeSource | Implemented Interfaces: | | ### Instance0 found in UCL: org.jboss.mx.loading.UnifiedClassLoader3@1f6d2e3{ url=file:/java/servers/jboss-messaging/server/messaging/deploy/jbossws.sar/ ,addedOrder=13} | | | ### Instance1 via UCL: org.jboss.system.server.NoAnnotationURLClassLoader@13caecd | | View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4089815#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...