and take a look in Home > Library > Preferences for anything that mentions the trackpad.
Drag the file onto the desktop and restart
i have a 13" mbp with snowleopard.
some 15 days ago, my trackpad could do all gestures just fine but it couldn't click.
i have the "touch to click" option turned off.
so, after pressing down on the trackpad like 10 times, it could only register one click.
as my warranty was valid back then, i gave my laptop to the service guy. he opened my laptop up, checked the trackpad and said it was fine and he told me that it must be a software problem.
so i erased the hdd and installed leopard and the problem was solved.
now my warranty has expired and the problem has come back.
whats wrong with my laptop ??
(i checked verified my disk and disk permissions, they're all fine)