I had a series 3 HD Tivo which had had been working perfectly for 1 year with a Panasonic HD LCD TV. I relocated it to a shelf and when I plugged the HDMI cable back in, the welcome screen displayed very briefly and was gone.
Eventually, I deduced that it was the HDMI port of the Tivo that was the problem. I had to Pay Tivo to send me a refurbished unit which resolved the problem.
So, apparently, when I moved the DVR, and reconnected the cables, I somehow fried the HDMI port of my Tivo. I did still have the TV on when I did this. Is that a known risk? Certainly, in the future, I will make sure everything is powered down when I work with these cables, but are there any known precautions one should take when plugging in / unplugging HDMI inputs that I ignored?