OMG, you’re going to laugh at me, but that recent nVidia driver (see this post) has screwed up my system. So I ate humble pie, completely uninstalled it and let the OS choose an earlier driver to install. I also had to use jv16 Power Tools to clean out the remnants of all that nVidia crap. This is particularly important, otherwise the driver that Vista chooses won’t install and operate properly.
So Vista reports that the nVidia version I’m using now is 7.15.11.6369 (September 11, 2007). If you want this driver, don’t bother to look for it at the nVidia website, it’s not listed there anymore. Go to this website which I found in a Google search.