Magic Trackpad Gestures Stop Working?

It appears to be a bug in ML (or possibly third party apps - see below). Basically, mission control is disabled. There are a couple of threads in Apple's support forums about this.

As an alternative to restarting, you can launch activity monitor and quit the dock. The dock will automatically relaunch and everything should be back to normal. Another less obtrusive fix that appears to work for most folks with this issue is to set a hot corner that activates the screen saver. You can set this up via the screen saver control panel. When you encounter the issue again, just move the cursor to the hot corner to activate the screen saver. No need to let the screen saver completely load. Just activate the hot corner and once the screen goes black and starts loading the screen saver, just swipe or click to abort loading and all gestures should be back to normal.

I have this issue myself and I think it's related to way some third party apps use the full screen feature. I use Movist and it's full screen browsing/video playback feature and it seems that if I don't quit Movist and the machine sleeps, Mission Control is DOA after waking the machine. If I quit Movist before the machine sleeps, things appear to be fine (so far).

Thank You

Thank you VanNess! A year after, still your reply is one of the best one can find on the net.