I'm no expert on Tivo but ....

I have quite a bit of computer repair experience and I will try to help ...The first thing I would suspect is that the 40 gig original drive is malfunctioning in some way. It doesn't have to fail totally to give you serious data integrity problems.

I don't know the exact problem that happened to your Tivo ( or how old it is), but it is less likely that the Tivo screwed it up, than it is that the hardware is failing (even if it is not very old - sh#t happens).

In my opinion the best thing you could do in this situation is start with a fresh drive, since all hard drives eventually go bad, and this is what might be happening to yours.

While you're at it you may as well use a slightly larger drive since 80 to 160 gig drives are not very expensive right now. Last month Seagate had a rebate offer - final cost $49.95 for a 160 gigger - for example.

This would eliminate the drive from the equation - which is the logical step to take in a repair situation like this (hopefully you can count on a new drive to be perfecto, but unfortunately now and then even a new drive can be bad - BUT ... this is unlikely)

My guess is that with a new drive the Instant Cake will probably work and you'll be Tivo-ing again in no time. :)

Good Luck!