Miraculously it now says on my dashboard that I've got 2 remaining favourite points (rather than 1 as it said yesterday) and that I need to find 7 geocaches to earn the next one (rather than 1). That's still not correct as I should earn the next favourite point after 6 (not 7) finds, but at least it seems that the process for calculating favourite points hasn't come to a complete halt.
I can only guess what's going on. I suppose that there is an asynchronous background process for calculating favourite points that must be buggy or has otherwise encountered problems, perhaps due to overload. It still doesn't seem to work correctly, yet some problems seem to vanish after a certain time lag.