Are you connected via HDMI? If so, have you tried component? It could be an HDMI handshake/sync issue.
It may also be worthwhile to powercycle the box after making the settings change to see where that takes you.
Adam; Yes on HDMI. I read about the possible handshake issue, but it had been working for 3 months since I got my new samsung. It's just strange that it stoped working.. Is powercycling the set top box just mean rebooting after making changes? I'll try that. Thanks.
Adam: I have the Motorola 6416 box. I've read the the new 7xxxx series may alleviate the handshake issue. Do you think it's worthwhile to investiagte swapping set top boxes?