If you can boot to Safe Mode then initiate System Restore, hopefully it's switched on, to go back to before you installed the new software and immediately turn off auto-updates.
Then phone Technical Support or use their online chat to get advice on what to do next.
McAfee relies on Internet Explorer being up to date and set to default settings. That's the only thing I can think of that would cause this as you said Windows is totally up to date.
Thank you for your comment.
I meanwhilst did this (reinstalled "old" version, gladfully I had saved it in first install; then disabled auto-updates etc.) but this isn't a favored solution to me (because I pay annually for updates, which I can't get at the moment).
I already tried to reach customer support, I wlll try again... Hopefully they will have an answer...
I'll post again, if I get any solution...
I had some sessions with technical support (chat, remote assistance) now but the problem still exists.
Steps taken were 1. full uninstall (with mcpr), 2. windows update checking, 3. reinstallation.
Now I am routed to phone support (2nd level), I have an appointment for wednesday with them. Hopefully they will have an answer.