Is it possible to access a CORBA object from a EJB? I am using VisiBroker 4.0 for my CORBA objects and J2EE 1.2.1 for my EJB.

Yes it is, you'll probably want to use the VisiBroker ORB from the EJB, to override the default ORB, use the following properties:

org.omg.CORBA.ORBClass=com.inprise.vbroker.orb.ORB
org.omg.CORBA.ORBSingletonClass=com.inprise.vbroker.orb.ORB
These properties can be set on the commandline (using -Dorg...) or using a file named orb.properties.