I tried those methods, but they never worked for me. Sometimes the calendars list in iTunes just went empty, and other times it didn't show all my calendars or only very old, long-deleted ones. Since the behavior was the same with my iPod and my iPhone, I could at least rule out a problem there. Today I finally discovered the culprit:
I am sharing my calendars via icalx.com, and it turns out that sometimes iCal simply "forgets" the URL I have set there and reverts back to .Mac, which I don't use. Reverting all the URLs to the correct values solved the problem immediately -- all calendars sync perfectly again now!
So if you're having the same problems, it might be a good idea to check the URLs of all those shared (and subscribed?) calendars in iCal.

