Clicking Notification Center Button Makes Dock Hang 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?
This appears to have been resolved by:


Forcing a shutdown (choosing shut down from the Apple menu would do nothing).
Resetting NVRAM / PRAM (hold command-alt-p-r during bootup, wait for three "bong" noises.
Upon startup, close all apps and reboot normally.