If you recall, I had problems with the swapfile sometimes taking several minutes to "quiet down" after switching among programs. You might also remember that it happened most often with Mozilla Firefox.
Well, guess what... Firefox has serious memory-management problems, and Mozilla is bringing out v7 not long after v6, to address this problem. I will hold off updating.
I also changed the swapfile to be only on F:, removing its other components from the C: boot drive. This seems to have helped, too.
Again, thanks for all the suggestions.