I have not figured it out what are the factors. Normally it happens installing the Monthly Update from Microsoft. I suspect it replaces one of the newer files with an older file that causes the Driver to roll back.. As stated, I have not figured out any rhyme or reason, but have confirmed it happens most every month since I first noticed it early this year. (I think the first one that did it was the December MS Update, but I missed it then, because an nVidia Driver came out the same time.

It does not matter if you do automatic updates or manual.. it will happen. I do manual, so I know to check after running the update.

I wonder if you remove the old Driver first, before updating to the new Driver if it may not happen.
For me, it has happened most months with my nVidia 7800, nVidia 6 Series cards... It did not happen with my Quadro, so it may be limited to specific card types.

ratscloset
aka John