This happens on a 2nd HD Digital Box (None PVR) upstrairs connected to Sony TV which is older and not HD. I have powered down and on again both the box and TV at different times, plus unhooked the Video 1 and tried it straight through the coax on Channel 3. In both cases, when the unit first turns on the screen is fine, then within seconds the bottom half of the screen goes solid black. My son's PS3 in Video 2 is fine. Any suggestions?