Since around 2 weeks, the close buttons of OS X windows and tabs are very hard to press. The issue is that clicking them will often do nothing until I move the window. The cursor hover will trigger the button to change visually which indicates the button is active, yet clicks are not registered until I move the app window (even if only by 1px) and click again. Only then the window will actually close. I have this issue with both my trackpad and external mouse. It only seems to affect close buttons (both the red close buttons of all apps and Safari/Finder tabs close buttons). I haven't installed new mouse-related or Finder-related software recently. Anybody have the same issue or have an idea of how to fix it?