Whenever I'm plugging in my external monitor into my notebook and changing the screen resolution to the maximum state, the desktop will get broken in a way:

• A third of the whole desktop space is not visible at all.

I can see the whole panel as well as the Unity side bar to the left, but the desktop space with all the windows in it is not completely visible. It's blanked out. In case of opening the Unity menu bar, I can type something in it. As soon as close the menu bar, the upper part stays visible and hangs:

Any ideas about that issue?