A message comes onscreen that says, "Shutting off in 30 seconds" or something similar, and the tv shuts itself off. Is there something in the setup menu I'm missing? I checked the 'Timer' function but it doesn't have anything programmed into it. It happens only when the tv hasn't been adjusted with the remote control for at least an hour or two. If we change the channel or volume or whatever, it'll stay on. But when we leave it alone, it'll time out and shut down. Is there anything I can change to fix this?