Answer:
It sounds like the Panel went out. If its within the 1 Year warranty, call and schedule a house call to get the problem resolved.
Either way try unplugging it for 30 minutes and this should reset the HDTV. Then plug it back in and turn it on. If the problem persists and there is no warranty, you can either get a TV Repair person to do an estimate or look at purchasing a new LCD or Plasma.
Hope this helps.
