i couldn't find that file...i found preferences.plist. I moved that to the desktop and tried changing the settings, still not working. The only gesture thats working is the one for the notification center.
hold the option key and click on the Go menu in the Finder.
go to your Library (this is your Users Library). go to the preferences folder,
find that file, move it to the desktop. reboot. see how things go...
you can also then go to the trackpad pane in system preferences, try making some changes there.
you have to do these things very precisely; i NEVER said to move 'some file called preferences.plist'; if you're not sure of something, ask again first..
always good to play it safe when doing OS-related things.