Recently when watching playbacks of recorded shows, the TiVo sometimes gets stuck for about a minute, with the picture frozen and it doesn't respond to the remote (although the red light may flash on the front panel to show that it's acknowledging a signal from the remote, albeit not acting on it). Then it reboots. This happened with 3 or 4 separate shows in the past week, and it is repeatable for any given instance of a recorded show. If I fast forward to the point in a show where it got stuck last time and press Play, it gets stuck again and reboots. However if I delete the same show and record a repeat of the same episode, it doesn't happen again when playing the re-recording. Any idea what might be causing this and how to fix it? Is this a sign of impending hard drive failure?