@sensico, after I had tried and couldn't get it to fail, I realized that I didn't have Gears running, and all of a sudden thought that might be the issue and sure enough it was. Funny though Gears and Firefox on my Mac get along just fine with wordpress. Go figure.
Gears seemed to have made a difference on my ThinkPad with XP (which has a slow 1GHz PIII processor and only 512mb of ram), but on my Mac laptop with the core 2 duo, it made little difference. I have it disabled on my Mac, and since I seldom use the ThinkPad, I doubt I'll re-enable it.