Looking at the release notes for AMD Catalyst 15.9.1 Beta, this is a known issue.
A black screen may be encountered on boot-up on Windows 10 systems. The system will ultimately continue to the Windows login screen.
As a temporary workaround to this problem, put your computer to sleep when you are finished. Wakeup should be instant and no black screen.
This didn't help my issue. Whenever I update the driver from 15.200.1062.1002 It will first act like it is normally it the screen flashes black once, then it goes back to the desktop, but after that it goes to a black screen where the only thing showing is the mouse cursor. When I shutdown the computer (manually) It won't even show the loading screen or login screen after I tried putting it to sleep. It just shows a black screen like it usually does before going to the login screen, with a mouse cursor and the blue loading circle nothing else. It rapidly switches between the version with the circle and the one without. Putting the computer to sleep doesn't help whatsoever. I have tried it in both circumstances, Just after the update and after a manual shutdown.