I'm using Ubuntu 13.04 and I guess ever since I updated it from 12.10 I've been having a problem with qt applications (VLC and K3B, specifically). Sometimes, when I open them, the title bar doesn't work. It is unclickable, so when I try to double click it (to maximise it), or drag it, or click on one of the control buttons, the window simply minimizes. The solution I found was to
Ctrl+Super+Up, so the window is maximized and the title bar disapears. If I restore the window again the title bar works normally again.
Here are some prints: