I think I can give you the answer
Open a terminal, then type:
sudo su -
enter your user password, then, as root:
echo options psmouse proto=exps > /etc/modprobe.d/psmouse.conf
Now, while your right mouse click should be working after a reboot, you can try doing it without a reboot, but it might crash your desktop. It didn't for me, so here it is, type in the same terminal as root:
rmmod psmouse && modprobe psmouse
hope that helps!
edit: ok, so now that the right button works, the touchpad section of the mouse settings disappeared, and so did my custom settings and the multitouch capability, which resulted in a slow mouse pointer and no ability to scroll. I think I'll write a bug report on this one.
edit2: I searched through the web, and apparently, there is some obscure way to fix this problem, but it relies on ressources and patches that aren't available so easily anymore. I fixed this problem for me by upgrading to quantal quetzal, which includes adequate (albeit not great) support for multitouch clickpads by default