There may well be a fault on the box, or the incoming signal, but whilst you are waiting for the forum mods to respond, try doing the following.
Press the Home button. Then press Thumbs up, Thumbs down, Play, Play. You should then hear a beep after a few seconds and the box should be a bit more responsive.
Also, if you still have a viewing card, remove it. It's not needed on Tivos anymore, and removing it can speed up the responsiveness.
No guarantees, but it might work.
Just another VM user trying to help, so no guarantees that my advice will work . If my suggestion is helpful, please mark it as helpful; it may help others. Just want to say "Thanks"? That's the Kudos button.