Minimize buttons are disabled when I connect an external monitor Whenever I connect an external monitor all the minimize buttons on existing apps get disabled (they are gray).  Why does this happen and how can I prevent it?
This is not expected behaviour, and without more information sounds like you might have a 3rd-part window management tool running that could affect the behaviour of existing windows.

If you run applications in Full-Screen mode, the "Minimise" button does get greyed out, if that helps