Hello Fabian Krüger,
Thanks for the answer.
I have also checked it by removing all jar files that are provided by JBOSS server from my /WEB-INF/lib directory. But problem seems to be same.
After searching lot in Google and putting question in different forums, I come to know that JBOSS 5.1 is very tightly coupled with JPA 1.0. So it is not possible to use JPA 2.0 with JBOSS 5.1 server.
So now I am trying things with JPA 1.0.
Let me know if you have any other ideas.
Thanks.
Amar