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
OS X Mavericks Will Be Available For Free And Download Today!
At this evenings keynote Apple announced that they plan on releasing OS X Mavericks for the amazing price of “Free” and don’t worry you won’t have to wait long either as it will be available later today.
Watch the ongoing keynote LIVE: www.MacReviews.com/Live
iPad 5 Keynote