As referenced here: http://wiki.jboss.org/wiki/Wiki.jsp?page=JBossWithJDK6 anonymous wrote : | Please note that JDK6 support is purely experimental in JBoss AS 4.2.x | As for JBoss5 http://wiki.jboss.org/wiki/Wiki.jsp?page=JBossVsJavaJDKVersionMatrix So, we do not officially support 1.6 for JBoss 4.2.x or for JBoss5. As for the warning message, this is simply informing you that the isolation level for the JMS DB is low. Typically this is applicable when you are running with the default DB, Hypersonic which is not recommended for production deployments. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4086966#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...