I am just starting this thread to let y'all know of the fix I used.
Problem: touchpad working fine in jaunty, not working at all after karmic upgrade. My laptop is a sony vaio, but the problem could be in all laptops.
1. Check what kernel you are booting into
If this is not your output, then you are using an older version (most probably from jaunty). You'll need to change the kernel you are booting into. This can be done by editing the default value in /boot/grub/menu.lst file.
Linux xxxx 2.6.31-14-generic #48-Ubuntu SMP Fri Oct 16 14:05:01 UTC 2009 x86_64 GNU/Linux
2. Search your 'dmesg' output for this:
3. Check if the 'psmouse' module is loaded at all:
$dmesg | grep mouse
[ 13.603905] psmouse: Unknown parameter `synaptics_resume_reset'
If there is no output of the above command, that means the touchpad module (psmouse) is not loaded.
$lsmod | grep psmouse
4. Look if there is a file called /etc/modprobe.d/psmouse.conf
If this line exists in the file, you have the same problem as me.
options psmouse synaptics_resume_reset=N
1. Comment out the line in (step 3) /etc/modprobe.d/psmouse.conf, i.e. add "#" at the start of the line.
The 'psmouse' module should be loaded successfully, and you should see a 'touchpad' tab in System->Preferences->Mouse
Please let me know if this fixes your problems. I'll try to help as much as I can.