Hi,
I think your ejb ref in "jboss-client" is defined wrong.
"ejb-ref-name" is the JNDI lookup name. "jndi-name" points to the global interface JNDI name.
So, according to your jboss-client.xml, you would have to perform a lookup for "com.tarangtech.mtg.authentication.AuthenticationBean" to get the Remote Interface.
Hope this helps. I don't know enough of your full sample to provide you with a full solution ;-)
Wolfgang
By the way: avoid the word "urgent" in forum posts, this will increase the chance of being ignored: http://catb.org/~esr/faqs/smart-questions.html#urgent