anonymous wrote : java.lang.NullPointerException | at org.hibernate.cfg.OneToOneSecondPass.doSecondPass(OneToOneSecondPass.java:135) | Looks like a bug in Hibernate which was fixed http://forum.hibernate.org/viewtopic.php?t=970823 But that doesn't explain why your application works on Windows and not on Linux. Are you sure there are no other server configuration changes between these two setups. Like jar files, classpath etc... View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4205912#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...