For the sake of those who may come across this in the search for their own solutions, I thought I should report back about the cause of this error. We had a couple of issues on the go, as it turns out: one thing that wasn't helping was our JBoss machine had run out of disk space. However, the main problem was that we had inadvertently included a jndi.properties file in our EAR deployment. I'm not familiar with the configuration in this file, but it was sufficient to completely hose our messaging in the manner described above. Removing it from our EAR solved the ClassCastException. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4021187#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...