I feel your pain. My Series1 DirecTivo died a few months ago and it had months of programming on 120GB drive. Not a biggie since I still have my HD Tivo w/ 750GB. So what I decided was to just use an old 80GB USB HD and reformat it. I went to PTVUpgrade and bought an image for about $20. Burn the image to a CD. Put the new HD in a PC and boot from CD. Burn the Tivo image to the disk in about 15 min. Put the drive back in the Tivo and I'm good to go.
If it's the motherboard, there are places like CSS, PTVUpgrade or Weaknees that can possibly fix it for you. With the introduction of Series 3, there's going to be a lot of older Tivos available to buy/cannibalize.
Alternately, you could go the HTPC route. I'm a Mac guy now and I found a $90 analog USB tuner for my Mac Mini that has a really easy TV guide. Plug in cable tv or antenna and you've got a DVR. VERY easy and converts files to PSP and iPod format in one shot. The HDTV USB dongle was just intro'ed at $150.
