I recently had a very interesting TiVo problem. Nothing in the FAQ was helpful and I was eve given the run around in the help forums. I was trying to record survivor and was getting audio only and no video. All the connections were correct and everything had power and it was not a local outage.
What happened? As it turned out TiVo was recording the High Definition channel. I do not have HiDef but it seems that Comcast was nice enough to give me the listings and let me listen to the audio. The show was on the same time but just a different channel.
If you are getting great audio and no video be sure you’re not recording the High Definition channel by accident.