I am new to ejb3.0, I just deployed a ejb3.0 app to jboss 4.0.3. when i run the client app, i got following error generated from my lookup codes:

java.lang.ClassCastException: $Proxy61
.......

here is the lookup code in my client:

InitialContext ctx = new InitialContext();
ShoppingCart cart = (ShoppingCart)ctx.lookup(ShoppingCart.class.getName());
......

I don't know why there is this exception and what is "$Proxy61"?