Recently, I upgraded to Mountain Lion for my Mac and guess what happened?
My lovely trackpad failed to work.
So after some painful searching through the goog, I manage to find the solution.
I am posting here so you (and I) will know what to do in the future.
1 - Hit "Command + Option + Esc" or if you are on a PC-keyboard like me, it is "Win + Alt + Esc"
2 - Terminate all processes and relaunch Finder
3 - Put your Mac into sleep mode by clicking on the Apple icon on the top left hand corner
4 - Wake your Mac by using the keyboard
5 - Restart your Mac by clicking on the Apple icon once again and select "Restart"
6 - Shut down your Mac by clicking on the Apple icon once again and then hit the power button.
This should make your trackpad work with gestures again.