This bug was detailed in Microsoft's compiled list of problems with the Windows 10 preview, specifically build 10061. Microsoft's Gabriel Aul confirmed the fix release on Twitter.
WU update released today for 10061. Fix for blackscreen issue after login: http://t.co/7J97uhp0dBWU update released today for 10061. Fix for blackscreen issue after login: http://t.co/7J97uhp0dB— Gabriel Aul (@GabeAul) April 28, 2015April 28, 2015
According to the Windows Support website:
"When you sign out of Windows 10 Technical Preview Build 10061 and return to the lock screen, you might see only a black screen with a responsive mouse cursor. Pressing the Alt+Tab keys or the Ctrl+Alt+Del keys has no visible effect."
It's a handy fix that will be welcomed by those who have dealt with the issues already. Should you notice the black screen when attempting to log in before updating your Windows 10 installation, Microsoft has shared a few tricks to try and work around the issue temporarily. When hit with the blank login screen, hit the CTRL key once to focus on the password field and type your password as you would normally.
