Our Tivo mystery was solved.
Yesterday it appeared as if our Tivo stopped working. I tried everything I could think, but the screen stayed black. I couldn't figure it out! Distracted the boys and got DH to come home and check it out. He worked on it for an hour, checking every connection and cord, but nothing made a difference. Finally, on a whim, DH checked the Menu button that controls the Picture.
Yes, you guessed it, A had changed the color on the tv so that everything was black.