This is an issue that's annoyed me for some time. About a year ago, the two-finger scrolling in Windows 7 on my Macbook Pro stopped working. I discovered that a fix for this is to open Bootcamp from the control panel, go to the Trackpad tab, tick and untick "Tap to click" and click ok. This has to be done every time the machine is woken from sleep or rebooted. I'm now using Windows 8 and encountering the same issue.
I've tried several different driver revisions, and none have helped. I'm sick of going through the motions. Has anyone got a solution for this?