gestures in lion- one does not work the rest do.

when i first installed the lion operating system thismorning i was able to swipe four fingers left to right and change between desktops.. now i can not do that. i have not changed anything that im aware of and really liked that feature. now if i want to change between desktops i have to swipe four fingers up then swipe side to side to change them.. its very strange because right after install the first thing i did was swipe four fingers to the left and the desktop changed lol now it dont.. is there any one with this same issue? was it a bug that wasnt supposed to work that way? any info would be helpfull.. i should mention i am running an imac i7 non thunderbolt model and i have that bluetooth track pad.