Well a little troubleshooting later this is where we stand.
Disconnectin my entire network from the cable modem and connectin the XBox directly to the cable modem gets a connection.
Connecting my DI-604 to the cable modem allows all my internal ethernet devices to connect to the Internet.
When connecting the Xbox to any internal switch, the XBox recognises that a cable is connected, but it fails to find the XBox Live! network.
When connecting the XBox to a free port on the DI-604 - the XBox does not even recognize a cable is connected. Even when turning the XBox off and the DI-604, and turning the DI-604 on after the XBox is turned on or before the XBox is turned on. (or any combination of the above)
The bottom line is the XBox will not see the DI-604 when connected to it, but will see a switch port but cannot route to the XBox Live! network.
GRRRRRRRRRRRRR!!!!!!!!!!!!!!!!!!!!!
[EDIT] Are you supposed to connect the XBox to the router with a cross-over or straight through cable? I have been using a straight through - I cannot imagine it needs a cross over.. but one never knows hey...