If I switch from ingame to desktop (hitting Windows key, sometimes unwanted hitted), mouse clicks don't work, and you cannot switch back to the game. I only found following solution: Strg+Alt+Enf, open Task Manager, using keyboard select the game, then 3x tab to go to button for ending process, hit space to end process. Then the mouse works again, and I can start the game again (hoepfully saved not too long ago).