After setting the org.hibernate to TRACE in logger i found this :
2011-10-04 18:10:23,559 TRACE [org.hibernate.jdbc.JDBCContext] (http-127.0.0.1-8080-1) TransactionFactory reported no active transaction; Synchronization not registered
how to fix this .......i have already set @TransactionManagement(TransactionManagementType.CONTAINER) on my stateless ejb.