I know this is a quite odd question, and I don't really know how to provide more elements to help you find a question. All I can say is that, suddenly, every window that has the chance to maximize itself will start maximized. One of the many examples is Chrome's preferences window, that should be a fairly small window but opens at full screen (1920x1080). Do someone have a clue?
Please help me in finding some more elements to get a proper solution.