And again today Windows 10 messed with my display driver …
Suddenly my screen turned black and after a couple of seconds my desktop came back, but a little later I realized that the ‘Sleep’ menu entry in the ‘Start’ –> ‘Power’ menu had been gone.
Running powercfg –a as recommended here revealed that the ‘Sleep’ capability had been disabled by my graphics driver. And checking my graphics driver revealed: it once more had been changed to ‘Microsoft Basic Display Adapter’.
I found 341.81-desktop-win10-64bit-international.exe in my download folder downloaded in October last year when this happened, ran it and let it re-install my NVIDIA graphics driver. I had to reboot – problem solved.