Why can’t a mouse interact with my Windows install but keyboard can?

I'm have a strange behaviour on one of my laptops running Windows 10 22H2. When I click into the active window, e.g., on the X (close button), the window title bar buttons become partly greyed out, and I can not interact with (any part of) the window at all. I can cycle through the windows with Ctrl + Tab , go to a different Window and back to the original one; the buttons have normal color again, but once I click (anywhere) in the window, I'm back to the previous state. Using keyboard commands, e.g., Alt + F4 to close the window, works, but only as long as I didn't click into the window. It s

Question by Albin on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.