This usually happens when I try to set priorities with task manager, but it can happen when I just right click, open with, (Ex. Paint.net). It will open the picture, but the "Open With Paint.net" menu bar will stay on the screen, and will be semi-transparent. The only way to fix this that I've fond is to log off/on, but that obviously means closing all open projects/apps. Can someone tell me what causes this? Or at least how to fix without re-logging?