I have a simple app that is connecting to a mssql db (not my choice), when I try and access the entity manager from within the bean I get a null pointer exception. There are no errors when I deploy the ear to the server (hot or cold deploy - no errors)

the class code is:

package com.wsmp.dao;

import java.util.*;
import javax.persistence.*;
import javax.annotation.Resource;
import javax.ejb.*;

import com.wsmp.dto.*;

@Stateless
public class StudentDAO implements StudentDAOInterface
{
 @PersistenceContext(unitName="wsmp")
 protected EntityManager em;

 public StudentDAO(){}

 public Collection<Student> getStudentList()
 {
 Query query = em.createQuery("from STUDENT s"); //Null pointer exception here!
 return query.getResultList();
 }
.
.
.

mssql-ds.xml file is (running though jTDS)

<datasources>
 <local-tx-datasource>
 <jndi-name>MSSQLDS</jndi-name>
 <connection-url>jdbc:jtds:sqlserver://150.104.62.27:1433/wsmp_t</connection-url>
 <driver-class>net.sourceforge.jtds.jdbc.Driver</driver-class>
 <user-name>x</user-name>
 <password>y</password>
 <min-pool-size>5</min-pool-size>
 <max-pool-size>20</max-pool-size>
 <idle-timeout-minutes>0</idle-timeout-minutes>
 <track-statements/>
 <metadata>
 <type-mapping>MS SQLSERVER2000</type-mapping>
 </metadata>
 </local-tx-datasource>

</datasources>

and the persistence.xml file is:

<persistence>
 <persistence-unit name="wsmp">
 <jta-data-source>java:/MSSQLDS</jta-data-source>
 </persistence-unit>
</persistence>

any help would be appreciated, I've tried a bunch of things and nothing works - probably have done something simple wrong...

cheers
Ray