Plasma TV & Lines on screen?? Filter for power?

It's highly unlikely that the interference is getting to the TV through the AC line. Hitachi power supplies are adequately filtered to prevent this. Chances are the interference is coming in from one of the inputs. You didn't mention which input you were using, so I'm going to ume this is coming in from the cable box. Check you cable connections and make sure they're tight. Beyond that, I'll need more info.