Could be something with the hardware itself. I had a satellite TiVo where one of the tuners was going bad and causing all sorts of odd behavior which I though was a bad hard drive at first.
Are you going to order the hard drive from weaknees and replace it yourself?
Probably. I few weeks ago when it was approaching 90% full, it kept freezing during playback, and rebooted by itself. I looked online and the hard drive was the culprit for that.