I recently bought a used Series 3 HD TiVo and picked up the two cards the "net" said I would need for dual tuner. Well, first thing, the box told me right off I had an "M" card, therefore slot two would be idle. Okay, so I call to get card activated, and I got everything but HD channels. So another call, they refreshed signal, then got no channels. Next call got all non-HD channels, and all the local (ABC, CBS, NBC) local HD channels, but no AMC, TLC, TNT, DISCOVERY, etc.... Just black screen. So I got TiVo tech on phone, they said TiVo diagnostics were fine. So, to make long story short, I spent a total of 33 hrs over 3 days on the phone (or Comcast chat) and am still left with all non-HD, and the few local HD's as previously listed. I have tried four different M-Cards, makes no difference. And it seemed that only 3 of the 18 Comcast techs I spoke to asked me for all the M-Card info (the rest said they only needed Card S/N.... Comcast said that if it was a fault of them not sending proper authorization signal, I would get error screens rather than black screens. So what do you think, bad tuner in the TiVo? It doesn't matter whether tuner 1 or 2, same deal. I am returning the TiVo, since it seems to be a unit problem, and have a Premier model (brand new) coming Monday. I guess I'll know for sure then. I can't express how angry (let alone flat worn out) spending that much time on the phone and getting up and down to change cards, reset unit, etc., and I finally told the last tech that they owed me big time. So I'm getting the second tier of HD (I pay for Started HD package), AND $20 off my bill for a year. Oh, and I even tried twice resetting the TiVo to factory default, erasing and resetting everything. Anyone have ideas on the problem, I'm nervous as hell to get the new unit and go through that horror again. Comcast is absolutely THE worst company I have ever dealt with, but my only choice here since I need high speed Internet also. Had my first question answered not only fast, but absolutely spot on.... If only Comcast could have that kind of talent/brain power working for them.... Have a great week all!