I tried your suggestion, blocking other sources by placing my body in front of the box. I could sit there and see the reflection from the red LED on the front of my peanut simultaneous with the yellow "acknowledgement" LED on the front of the Tivo box. I was just popping around the menus at high speed, up, up, up, down, down, left, left, left, right, right. All this while holding the remote 6" from the box.
It worked pretty well. Most of the time. But I would say at least 20% of the time, it would simply miss the key press. The remote LED would light up, so I know the remote was getting the button presses. But the acknowledge did not happen at the Tivo box. It simply missed the button press. And often if it missed one, it missed two or even three button presses in a row. And then would just start catching them again.
It's all pretty annoying. So is this normal with Tivo? As I said before, my first box did not do this for several months after purchase, and I presumed all along that when it started, it was due to a software upgrade. But this newer box has acted this way from Day 1, which was about a year ago.
Thanks for any help, or simply info, you can throw my way,
Norm