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 Mountain Lion 10.8.5 Beta Now Available To Developers, Retail
Apple has officially seeded the first beta of OS X Mountain Lion 10.8.5 to developers and Apple has asked developers to focus on several improvements including WiFi, Graphics, Wake-from-sleep, and PDF Viewing and Accessibility.
The company has also seeded the release of 10.8.5 to its retail teams for extended testing in a more controlled environment and the release is expected to fix several other bug fixes.
OS X Mountain Lion