I saw 1 thread about this, but I think my situation is different. After a few hours on inactivity and my iMac going to sleep, when I wake it up and type in my password only the 2 finger scrolling works. No other gesture works until I restart the computer. It's pretty annoying considering it ONLY happens after I wake up the computer and put in the password. This didn't happen at all in Lion. 4 finger swiping, 3 finers + thumb pinching etc doesn't work.