Thanks for the feedback.
Could you run Utilities/Console and search for "abmod" in system.log.
If you get the following line:
ApplePS2ALPSGlidePoint: ABmod, Loading Clicking Settings at Boot: 1, 1, 1
You have installed the driver correctly.
If not, install the full VoodooPS2Controller.kext from the insanelymac link in the previous post.
If you have the driver installed, I think it's a 2 finger scrolling calibration issue.
To confirm this for me, could you use 3 or 4 fingers to scroll?
So to increase the area touched on the touchpad and try moving your fingers up and down simultaneously to scroll.
If this works i shall provide a way to calibrate this driver to suit different trackpads and finger sizes.
I look forward to your feedback.