Today out of the blue in mid use (no restarts, updates or changes) my 3 and 4 finger gestures stopped working. Google led me to this thread: http://discussions.apple.com/thread.jspa?threadID=2223030&tstart=0 Seems several people had this problem and there are two solutions posted in that thread. The one I tried first, and it worked, was to create a new user account and switch to it. The gestures worked fine in that account so I tried my original account again and all was good. I deleted the new account and things are still back to normal so far. Weird.