Hi guys. For some reason my RCA Scenium HDTV goes black and says "Unusable signal" on every channel. I think this is because it's trying to display the channels in 480i SD (it says in the top right), but I can't seem to figure out how to change that. I have left unplugged for several days, and still it does not work. Also, when I first turn to a channel, you can hear the sound for the first 2 or 3 seconds, then it goes black and says unusable signal. Any help would be appreciated, thanks.