On one user account on one of my family macbook air machines (all with the latest version of Lion) the two finger trackpad swipe left and right to switch back and forth (e.g. between pages in safari) does not work . The three finger swipe and all other gestures work like a charm. Any tips how to make the two finger swipe work again?
Others seem to have this problem, too: https://discussions.apple.com/thread/3313418?start=0&tstart=0