I was looking for a solution here and the answers were only to open the 'System Settings' and to change the settings there. This was no help for me but then I found this: Touchpad not working on Dell XPS L501x I followed the instructions and reloading the kernelmodule with that specific option helped me out (I run Oneiric on a Sony VPCEB1S1E). Now the question: how to set his Option permanently?
You can create a new file in /etc/modprobe.d, e.g. /etc/modprobe.d/psmouse.conf and put this line into it:
In case you don't know how to edit a file as root, you can use this command in a terminal: