One of my cablecards recently started losing some upper end channels, showing a blank screen. All the info in the CableCARD Menu screens appear normal. When I use the Test Channels option, it will come back but later on it will be lost again. The funny thing is that today cablecard #2 (a new M-card) is having this problem, when all week it was cablecard #1 (an older S-card). So now I'm not sure if the issue is with the cablecards or my Series 3 Tivo.