Same problem... I've set the 480p and now is everything messed up in the screen.
QUOTE(apetastic @ Jun 22 2005, 06:23 PM)
Unplug the HD cable and put in the standard A/V cable that came with your Xbox. The Xbox detects what cable is inserted so it should revert back to a 480i picture. You can then disable HD support and plug in your HD cables again.