TiVo Series 3 audio goes out

I have the first gen series 3, and until about the last couple of months it has been working flawlessly. After about 20 minutes watching a recorded program the sound will completely drop out. If I hit the remote 'play' it will come back on, but only for about 30 minutes or so. Could this have anything to do with the HDMI connection?

Thanks in advance,
Mike