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