Enter your password - a surprising trick that works. From there you can adjust the size, color, and position of the text. Click on the text tool within the toolbar and then click on the photo to create your text. I always disable the option to Lock on Session End as this is sometimes also a problem, but I cannot find a pattern that causes the black screen.
If your Mac appears to be stuck on a blank screen, follow these steps. If your Mac starts up to a blank screen A blank screen (black, gray, or blue) should appear once or more during startup.