try typing your log in password and pushin enter if you have one, if you dont then just try pushing enter or clicking around the screen. It happened to me on Windows 7, would load up and would get to a black screen with just a cursor, which I figured out was the login screen, I assume this may be your issue too. It fixed itself after I had logged in by typing the password then pushing enter.
Someone also said you might be able to ctrl+alt+del, however I don't remember that working. If none of these work for you, then Google is your best friend.
