Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
The Signs and White Curtains Go Up At Apple Stores For Steve Jobs Tribute –
As we reported earlier in the week that we expected the Apple retail stores to show for a few hours today to join in the celebrations of Steve Jobs live and also pay tribute. That has now been confirmed by these pictures which show the signage telling customers the store will be shutting for a few hours , In the other picture you can also see the white curtains being raised at the front of the stores as the event is employees and close friends only.
(Via https://twitter.com/#!/buffer/status/126700246079246336/photo/1/large )