I'm working with JBOSS 4.2.3 and JPA/Hibernate, and Postgress. I managed to create my tables, but then I created a new class to be mapped as a new tables but when I deploy the jar,I got the following error: Problem starting service persistence.units:unitName=JPAResources javax.persistence.PersistenceException: org.hibernate.HibernateException: cannot simultaneously fetch multiple bags at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Con figuration.java:720) at org.hibernate.ejb.HibernatePersistence.createContainerEntityManagerFa ctory(HibernatePersistence.java:127) at org.jboss.ejb3.entity.PersistenceUnitDeployment.start(PersistenceUnit Deployment.java:246) .................. ................ --- MBeans waiting for other MBeans --- ObjectName: persistence.units:unitName=JPARecursos State: FAILED Reason: javax.persistence.PersistenceException: org.hibernate.HibernateException: cannot simultaneously fetch multiple bags I Depend On: jboss.jca:service=DataSourceBinding,name=PostgresDS --- MBEANS THAT ARE THE ROOT CAUSE OF THE PROBLEM --- ObjectName: persistence.units:unitName=JPARecursos State: FAILED Reason: javax.persistence.PersistenceException: org.hibernate.HibernateException: cannot simultaneously fetch multiple bags I Depend On: jboss.jca:service=DataSourceBinding,name=PostgresDS JPAResources is the name of may persistence-unit JPAResources.jar is the name of the jars containing the classes and de pesistence.xml file I will apreciate any help you can provide me. Thanks View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4193040#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...