I'm back online after a few weeks suffering from a serious virus infection.
This one was devious. It prevented any connection with any of my anti-virus software websites for updates, it prevented most anti-virus software from even running, it kept popping up Internet Explorer (which I never use) windows. It pretty much had me dead in the water.
I've managed to remove most of this infection manually, but vestiges of the virus remain. Anyway, I'm back online now and working more or less normally.