Unable to use 3rd party ORB / IONA

Hi,

I am unable to use 3rd party / IONA orb in my j2ee application. I am initializing ORB as below:

private static final Properties orbImplProps = new Properties();

static {

orbImplProps.put("org.omg.CORBA.ORBClass", "com.iona.corba.art.artimpl.ORBImpl");

orbImplProps.put("org.omg.CORBA.ORBSingletonClass", "com.iona.corba.art.artimpl.ORBSingleton");

} 

////

orb = ORB.init(null, orbImplProps);

But the instance returned by above init call is: com.ooc.CORBA.ORB i.e. orbacus orb implementation.

Please help. Thanks