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 iTunes 11.1 Including iTunes Radio To Developers
Apple has just seeded iOS 7 beta 4 to developer and now it appears are seeding iTunes 11.1 beta to developers. A big new feature introduced in this beta is iTunes Radio which we heard about at WWDC 2013.
iTunes Radio is still only available for developers in the U.S which is the same circumstances as iTunes Radio integration in iOS 7