Comment 70 for bug 1238194

As recently as kubuntu 16.04, it is not fixed if the user switches to the nvidia video driver.
I tried several times to switch back to nouveau and back with no luck.
About 95% of the time I'd get a blank screen; no prompt. The rest of the time I'd get the unlock prompt but keyboard input was ignored.
The fact that the update manager is also broken in kubuntu 16.04 doesn't help. I was able to switch back and forth using 'ubuntu-drivers devices' and apt-get. I also tried 'update-initramfs -u' incase hid/usb was somehow not there.

What finally worked was to change grub to 'quiet nosplash' -- get rid of the splash screen.