Vista MCE won't let me list both HDTV and Cable channels at the same time

I realized a few days ago that the HDTV channels I had listed in MCE mysteriously disappeared sometime in the past weeks. The channels from basic cable are still in the program guide, and they all still work, but Vista won’t let me add any channel that isn’t numbered between 2 and 62.

I’ve got an ATI HDTV Wonder for the antenna and an older Hauppauge WinTV350 for the old cable. They both work, because the HDTV worked earlier, and now the cable works.

But the bizarre part is that I can’t find ANYTHING about it online. Maybe I’m just suffering from massive internet failure, but I can’t find anything in Google, on The Green Button forums, or Yahoo, or wherever else I can think of, that actually talks about anything like this.

I’ve heard somewhere that you’re not supposed to be able to use multiple tuners in Vista unless they are the same model of tuner (mine are not), but I can’t find that anywhere online. Nor can I find a setting in the Vista MCE interface that lets me configure my tuners. It just gives me the option to tell them whether I get my TV from an “antenna” or from “cable.” What gives?