Last two months Comcast is dropping HD channels at random. Couple days later, the channels reappear. Comcast claims we cant get HD on our TIVO Premier Elite with M-card. - yet we have been getting it all year. I'm wondering if Comcast in North GA. is now trying to use SDV - and we dont have a tuning adaptor or box of any kind. The dropped channels are still available in SD. Sometimes the DVR diag. screen shows signal levels at 93 - and other values also OK - yet screen is blank. Other times, DVR diag. show blank values and Current Tuning State = Not Tuned: Wrong Card State. No one at Comcast seems to know anything at all. Again, could it be Comcast is now trying to use SDV in North Georgia. Anyone know?