I think I found a bug in LibreOffice 126.96.36.199 and Unity in Ubuntu 15.04. If you create a new document in Libre Writer and completely filled the page in any text and then select it by pressing сtrl + a, and then hold down the Shift key and start scrolling text on the page up and down using the scroll button of the mouse (Continue to scroll until you hang up, he is not the first time hang.). After that, the Unity completely frozen and does not do anything. Only helps restart Computer. This crash Unity I managed to play many times, as I am working in LibreOffice. Please, try to reproduce the problem on your computer.