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Just reset the box. Unplug box. Press and hold menu button on remote and continue to do so as you plug box in. That will take you to the BIOS. Change what you need to there and save. Reboot box and should be good to go. I have done that a few times to solve the same problem when I was first learning this game in the beginning. Make sure while in the BIOS that box is set to "Boot from NAND".
 
I know that. All the settings can be access through the bios weather you reset the box or not. In the bios the video is in a default mode and you can see it no matter what video mode the thing got into. Then just tell it whatever mode for video you want and exit the bios. Takes two minutes max. No hassle. Done. I saw all these posts and simply wanted to share a short cut. Have a great day!