I'm not sure what happened overnight but this morning my version of Navigatrix is playing up something chronic!!
Does it auto update everything to the latest version much like Microsoft Updates?
A lot of my icons have changed.
I've lost the 3 icons up the top/rt corner on EVERY program so I can't close windows or end programs.
I don't get any icons of open programs on the status bar so I can't rt click and END opened programs.
The curser moving around the screen has changed to a red cross.
I ended up killing the computer with the power button & then booting into Windows 10 to write this post!!
Any ideas?

Your problem is NOT a version problem as described in the first post or subjet.
If an admin can move to the best place.

Anyway, Open another thread to your problem and add if you have W$ on the same HDD or not in dual boot.
Add your display card (video) informations too.

Have you install and check with ClamTk if you have viruses or malware in your system (full HDD).

To close a window is easy, just "Alt+F4"keys on your keyboard.

It seems to be a theme manager problem or LXDE corruption file in your session.
I have had this on my laptop, using Xubuntu and I've solved it with this command in Terminal or Console :

If it does not reboot, stop and restart manually.

Nota : I used xfdestop command because Xubuntu, for Nx it should be different.

It can be another problem, very easy to do and very difficult to find...
Hitting "F11" make this by removing icons on top right of windows and removing status bar or start menu... Hitting again "F11" return to normal configuration. This problem can be caused by ads opening windows in full mode too...