I was having the same issues with my touchpad which is also ALPS (dell d610). Here is how i fixed it. I simply tweaked the kext named VoodooPS2Controller.kext a bit and forced all the scrolling flags to true. Also I changed the default mouse pointer speed values so the pointer is much smoother and doesn't jump anymore.
Download the modified VoodooPS2Controller.kext from here:
http://www.4shared.com/file/149362318/6417b7d5/VoodooPS2Controllerkext.htmlNow all you have to do is extract this newly downloaded kext to your desktop and then copy - paste it to /System/Library/Extensions/ and overwrite the default VoodooPS2Controller.kext that is already residing there.
You may get a message that this kext was not installed properly and bla bla after you replace, just ignore them and hit OK everytime! Now let's do the final step.
Open terminal and type the following:
sudo -s
[your password]
clear
cd /System/Library/Extensions/
chown -R root:wheel VoodooPS2Controller.kext
chmod -R 755 VoodooPS2Controller.kext
cd /System/Library/
rm -rf Extensions.*
diskutil repairpermissions / {this step may take some time till it reaches 100% so be patient}
reboot
Now you have fully working scrolling as well as a much stable touchpad. However you still won't be able to open the customizing panel from preferences. But who needs it now anyway?

Hope this helps.