@blackbird71 We have all done all the things you suggest and more, many of us with Carbonite techs looking on as well.
To be clear, Opera, in my case, did not "install itself." I installed and then uninstalled it when it did not work well. And when the popups began, I started the aforementioned Microsoft thread, in the hopes that I'd discover what went wrong.
After several weeks of reading replies, I reached out to Carbonite, where a tech took over my computer and gave me the info that you've seen posted here earlier. Which was that the Opera uninstall apparently takes with it a component that some other programs require to start properly.
I did not install anything other than Opera before the problem began, nor is it a Microsoft update issue. We just need to know what that component is and how to get it back, if possible.