"jaikiran" wrote : 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... Yes the two configurations are the same (zipped and unzipped the whole jboss directory including the deploy directory with the web application). With your suggestion and the information I've found in your blog the bug seems to be resolved now. For anyone facing the same problem, I've done the following: 1) I' have created a "lib" directory in the web application ear directory 2) I put in the lib directory the following jar files (according to the hibernate compatibility matrix): hibernate (3.2.6 GA) hibernate-annotations (3.3.0 GA) hibernate-commons-annotations (3.3.0 GA) (contained in the lib directory of hibernate-annotations) hibernate-entitymanager (3.3.0 GA) hibernate-search (3.0.0 GA) hibernate-validator (3.0.0 GA) lucene-core-2.4.0 (2.4.0) Thanks for your help. A. P.S.: it's incredible that the bug affects only the Linux system.... View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4206210#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...