Hi, I've had my plasma for less than a year now and all has been fine up and til now. When the Plasma is running for an hour or so, the screen shuts off automatically, with this electrical noise. I have to turn the Plasma off from the switch on it wait a few minutes, then it will come back on. Has anyone experienced this ?? What is causing it ? It's covered by John Lewis, anyway, but want to check what the problem is first ? Any help guys ?