This has been going on since this past Friday. I simply don't understand why Apple can't acknowledge the issue so their customers don't waste their time trying to solve a problem that is most definitely theirs. Just have some part of their website that lists "known issues".
Mine works now. The reason companies don't admit they have a problem, is that people who don't have the problem or didn't notice until advised will start calling and demanding answers before they have one.
I have the same problem not sure when it started but it recent. I've tried the solutions above but all its done is allow me to refresh the stations and show new ones from what I can see. Not sure what's going on most of the channels are unobtainable.
I don't think that there's anything you can do...I think that there's some back end maintenance going on that they're not making us aware of because I was getting the same message on my Mac at home and at work.