Currently getting the unexpected problem (C501) and continuous reboots, If i try to watch a recoding or change channel. Tivo seems to stay on longer if i'm on the menu screen with a small tv window about 3mins worth if i go full screen TV it reboots immediately.
I'm really sorry to hear that you've been experiencing this issue with your TiVo®, I really do understand how you feel regarding this as I had a very similar problem a few years ago, it was down to a faulty hard drive with in the TiVo®.
Upon looking into things from this end, I can see that since posting, you've spoken to our fault centre and a technician has been out and changed the TiVo® for you. I sure hope all is well now, let me know.
I understand that it can be frustrating when a TiVo® is changed, whilst we are unable to save any of the recordings, there are things like series links, wish lists etc that we are able to back up. Why not check out http://virg.co/boxswap to learn how to back up some of the settings you had - these options are available for a few days after the box is swapped so this may still be an option for you.