could not dereference object when running the EJB

[vitalstrike82]

Hi,
I'm using jboss4.0.3. I want to reference my jsp page to EJB but get a "could not dereference object" upon running the jsp with this as it went into the catch exception instead of looking up to the EJB:

try {

 objref = initial.lookup("java:comp/env/ejb/MyMusicCart");
 System.out.println("lookup success for ejb/MyMusicCart");
 // a reference to the home interface is shareable
 cartHome = (MusicCartHome)PortableRemoteObject.narrow(objref, MusicCartHome.class);
 System.out.println("created MusicCartHome object");

 } catch (Exception ex) {
 System.out.println("Unexpected Exception: " +ex.getMessage());

My web.xml

<ejb-ref>
<ejb-ref-name>ejb/MyMusicCart</ejb-ref-name>
<ejb-ref-type>Session</ejb-ref-type>
asg.MusicCartEJB.MusicCartHome
asg.MusicCartEJB.MusicCart
<ejb-link>ejb-jar-ic.jar#MusicCartBean</ejb-link>

</ejb-ref>

Can anyone encounter this problem before? Please help