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
Apple Release IOS 5 Beta 7 to Developers
iOS 5 beta 7 and Xcode 4.2 with iOS 5 SDK beta 7 are now available for Apple Developers. You can get access to the new beta by going to Apples Development center or Apple as also allowed developers to install iOS 5 beta 7 using over the air software update from devices that have iOS 5 beta 5 or later installed.Apple has told all of its developers to download this version to take advantage of the following features iCloud Storage, Newsstand Kit, Core Image, GLKit, Twitter, and new Game Center APIs. Apple has released iTunes 10.5 beta 7 and Xcode 4.2 beta 7.
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