Because I have the same userinit problem:
At the Welcome to Setup screen, press R to repair using Recovery Console.
Select the operating system to log on to by number...usually 1...press Enter.
When prompted for the Administrator password, leave it blank and press Enter.
But when I get to the Administrator password step and leave it blank it says this is incorrect. I am the only user and I don't think I ever set an Administrator password or anything and none of my usual passwords works. Is there a generic Admin password or anything that might work, or some way for me to recover this? Thank you!