Same here!
I can't log in right now. Every time I'll get the same error message: "Login failed. Please check your userid and password."
The log in screen also slowed down my Mac like hell...wasn't really usable anymore. As a guest (even when I tried "Sign in" from the main screen again) everything was fine and smooth.
Maybe something with the blur effect? CPU usage was around 20-30% and dropped to 5% as soon as the blur was gone...
I'm on Mac OS X 10.9.2 on a Mid 2009 MacBook Pro.
Hope that helps! If you need logs or something, I'm happy to help! Keep up the good work!
