Multi touch gestures problem

I have a 2010 21 inch imac. I have upgraded to mac os x 10.7 also. I wanted to take control of all of the multi touch gestures, and so I bought a apple magic trackpad. It has been working very well for me so far, but this morning a problem arose. I was using it just like normal, and I was switching in-between a few of the different desktops that I have, which is three fingers on the track pad and swipe to either side, and it was working fine until, for some reason, all of the gestures do not work anymore what so ever. The only gesture that works is the scroll with two fingers gesture. Now I can no longer swipe in between my desktops. And I can no longer bring up mission control. Does anyone know of any reason that this would be happening? Thanks for the help.

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