anyone else notice their tivo failing to record a complete show ?

a few times now, my tivo just doesnt record the entire show.
it stops at some random point during recording.

the time bar at the bottom of the screen still says 1hr for example, but the green bit might only be 10 or 15 minutes.
so it's like it knows that the recording should have been for the whole hour, but just gave up recording for some unknown reason.

mine has done this on a number of occasions now.

any ideas ?