I am using OS X Mountain Lion (on a MacBook Pro). I have noticed that sometimes if I try to close a window by clicking on the red close button or if I try to click a toolbar button (like get new mail in Mail), it doesn't always register the click. Clicking still works as I can click elsewhere, and I can still use keyboard shortcuts to close windows, and if I wait a few seconds clicks on the toolbar will register again. Has anyone else come across this? Is there a fix?