My problem with gestures with my magic trackpad on my Mac Pro is:
Upon a fresh restart, when I do a three finger swipe left(back a page) or right(forward a page) in both Firefox and Finder, it would work fine.
However, after a certain period of time (I still haven't determined it), three finger swipe would no longer work, UNTIL, I use two fingers to scroll(even just a short 1mm drag on the magic trackpad), then the three finger swipe would work again. It would work until I switch windows (like from Firefox to Finder), and then the problem comes back, and i have to scroll with two fingers before three finger swipe activates...
This problem can be replicated without fail... kinda annoying... I dont want to have to restart my computer every half hour...