I have a new Series 3 which I've had activated / running for about 48 hours now. Running on 2 cable cards with HD service, Cox Cable. Problem is, the screen goes black on me intermittently for short periods, with no rhyme or reason. It is as if the output is interrupted somehow. I don't even know where to start diagnosing this problem. It happens over HDMI and composite connections. When it happens, the audio continues un-interrupted, even in 5.1 on an HD channel, so I think its a video-only problem. Is this likely a problem with the TiVo, Cable cards, or service provider (Cox)? Any suggestions?