Ooops, didn't see that GOS forum. I'll post again there.
Also I'm not in the US, so ringing is my last option . . . I thought this might be a common problem, but in fact it looks not.
Thanks for the replies.
Well, I recently had the problem, and a phone call to Gary (actually, Mrs. G) solved the problem easily and quickly. My problem was a cracked disk, and I would bet that if you examined yours closely, you might find some problem around the hub. I expect an email to Gary would yield the same nice results as my phone call, except that you would miss the chance to talk to his nice wife!