I'm experiencing a very strange issue on my Mid 2012 Retina MacBook Pro with OS X 10.8.5. All of the sudden I discovered that I was unable to command-tab between open applications, the dock would not unhide, I could not open notification center, and I could not three-finger-swipe between desktops. I discovered that force quitting Dock from the Activity Monitor would remedy the problem, but if I click the Notification Center button, the problem returns until I force quit Dock again. The Notification Center does not slide out when I press the button.
I don't click the Notification Center button often, and I know that this problem has started without me clicking the Notification Center button at least twice. However, I did notice that it seemed like this started when I received a Mail notification this morning.
Does anyone know of a solution to this problem?