I have no ideas because, whenever I have it, i just go to a sat channel and it comes back instantly, no lock ups etc.... My 811 is working great.
here is some more recent discussion on it in the stuck P284 update thread.
But here are some preliminary questions:
Does it happen when you're watching off the antenna for a while then switch back to satellite? If that's the case as soon as you go back to satellite it should come back...