EntityManager not getting injected

[rorschach]

I'm working with version 4.03SP1.

I have a stateful session bean

@Stateful
public class ActivityManager implements Activity,Serializable {

 @PersistenceContext(type=EXTENDED,unitName="em")
 private EntityManager em;

...

My persistence.xml

<entity-manager>

 <name>em</name>
 <provider>org.hibernate.ejb.HibernatePersistence</provider>
 <jta-data-source>java:/MSSQLAppDSInterop</jta-data-source>

 <class>com.xpel.hibernate.UserAccount</class>

 <properties>
 <property name="hibernate.dialect" value="org.hibernate.dialect.SQLServerDialect"/>
 <property name="hibernate.transaction.manager_lookup_class" value="org.hibernate.transaction.JBossTransactionManagerLookup"/>

 </properties>

</entity-manager>

When any methods on the bean are called, the EntityManager "em" resolves to a null value. I have a similiar project where this works flawlessly using the same libraries and app-server instance.

Suggestions?

[rorschach]

The JNDI lookup does work however.