display
My laptop recognises external display devices if I connect them before booting the system, but many times it doesn't if I connect while the system is running. In this case, rebooting naturally solves the problem.
Is there a way to force Ubuntu to detect external displays? Opening up the display menu and pressing "Detect displays" does nothing.
The monitor cable was loose.
When I removed the cable and firmly plugged it in again, everything suddenly worked.
The monitor was recognized, and now I am using my previously desired resolution:
I feel kind of silly, because I never thought merely touching a loose cable would be of any help.
I've received this black screen with cursor myself (I use 4 monitors, and so unplugging them happens often).
However my fix was to correctly install my GPU's drivers.
Since your laptop apparently has an Intel HD 3000 series GPU have you tried installing up-to-date drivers? The Additional Drivers tab in your Software & Updates part of System Settings would be a good place to start.
Best Answer
Actually, you don't need to log out. Simply going to a VC with ctrl-alt-F1, restarting x with
sudo service sddm restartand and going back to your graphical interface with ctrl-alt-F7 (or F2) should do it.This way, you don't lose all your windows...