Also, I can't click on a tab and open it. I have no control over tabs

Did you try reinstall firefox?

You can try to start firefox in safe mode to see if the problems happens

https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode#w_how-to-start-firefox-in-safe-mode

The System Details list shows you use Firefox 52 (ESR) ?

Any specific reasons why you use this old outdated Firefox version ?

Are you talking about the close X on individual tabs or the close X to close the window (i.e. the maximize and minimize and close window controls) ? - - - - Make sure you run Firefox in desktop mode and not in tablet mode.

• https://www.top-password.com/blog/windows-10-switch-between-tablet-mode-and-desktop-mode/

Restarted in 'Safe Mode' and everything was as supposed to be. Restarted Firefox then and the same, everything was the way it's supposed to be. SO SIMPLE. Thanks!

I use the ESR because the new one doesn't like my add-on of "Tab Mix Plus". This add-on I can't do without. One that you people should look at and come up with a clone of it and I'd go forward. Seems all the new 'upgrades' leave something BETTER behind that we like. Well, I don't like that! This old version works just fine for me, I don't need to do the so-called update.