Currently Being ModeratedNov 9, 2012 4:56 AM (in response to cwiens)
Note: Since i first posted this solution its never happened to me again.
I had this problem but I found it was the settings that changed when mountain lion was installed.
Mountain lion changed my three finger gestures to four finger gestures when swiping between full screen apps.
I found there were extra settings. Apparently when installing mountain lion my three finger gestures were changed to four finger gestures.