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 7 Beta 4 – Download It Now!
As expected Apple has just released iOS 7 Beta 4 to developers. Beta 4 is now available via over-the-air which you can do by going on Settings > General > Software Update.
iOS 7 beta 4 should be available by the Developers Centre soon after suffering and full outage after a reported attack. With iOS 7 public release expected in the fall it is certain that Apple will be focusing on cleaning up the interface as well as everything under the hood.
One thing which is clear that has changed is the direction to slide on the lock screen is now a lot more clear.
We will keep you updated if we find any new features or big changes but if you beat us to it be sure to let us know on Twitter or Tips@MacReviews.com