T440S strange trackpad problem - can anyone help?

Hi all - wonder if anyone can help?

I have a very annoying intermittent problem. Before I log in to Windows (8.1 professional), the trackpad works and the mouse pointer moves about the screen. This is the case too for the first couple of seconds (until drivers are activated?) - after that, the trackpad works for clicks but not as a trackpad (I have to use the red nipple).

If I go to mouse properties in the control panel, I have only two options available for Pointing Options - use Trackpoint Only, or Use Classick Trackpoint mode only. Sometimes, after a reboot or hibernate (but not sleep), I can actually choose trackpad as the first option, instead of the other two - and it works! But then the next time I reboot or wake from hibernation, there are three options - but the first one (where the trackpad one should be) is blank!

In their infinite wisdom, IBM (or whoever now 'supports' Lenovo) advise me that the only course of action is a complete reinstall. Much as I'd love to spend three or four days backing up, reinstalling, reupdating data, trying to find or remember login and certificate information, tweaking settings yada yada yada... I'd rather explore every option first!

I have had this problem for about three months, and my trackpad was very recently replaced - it worked brilliant for three days, then this problem recurred

Does anyone know WTF is going on??

cheers
Benjamin