I have the same problem on my 50' Panasonic Plasma that was posted by srobsrobusa on 6/8/08 - black lines or black bar appearing 2/3 down on screen. The TV repair guy said it was being transmitted by my cable service. I have since switched to Verizon Fios and still have the problem. It usually happens when the TV has been on for an hour. Now I'm starting to think it's the TV and not the signal.