Just more questions I guess, but they may help to clarify your situation...

Are you using 10/100 ethernet connectivity, or phoneline/HPNA?

Is there more than one DHCP provider on your network? I.e., are you running A.R.M. windoze server program and do you also have a firewall/NAT device that also does DHCP? Are any of your other [Linux/Windows] boxes configured to be DHCP servers?

Is it possible your wiring got chopped somehow? If you're using phone line, you might stick another phone/handset on there to verify connectivity. Otherwise, you might put another computer on the line if you're using Ethernet at the Rio site. Of course, the fact that your Rio presents a link-level light probly renders this question moot.

Do you think your server side stuff could be messed up? When I used the provided ARM server, I noticed that the Rio Receiver often could not connect without rebooting the PC on which ARM runs. It was not enough to restart the ARM application, I had to reboot the entire PC.

Those are a few questions; I'm sure others will have more...