Sadly this is an issue known to TiVo that they refuse to look into. I suspect that they're eventually going to turn off the download spigot. That's why I've gone back to recording OTA via a regular HD tuner. Either TiVo or Comcast will do something that breaks the file, and they convert high-bitrate 1080i channels like NBC and CBS down to bitrate-starved 720p. Besides, MPEG-2 may be wasteful, but it's way less finicky than AVC.