I have late 2011 MBP with Yosemite OS. Lately (~2 weeks?), I've noticed that I have to log in twice! The first time, the password appears as black dots and the screen appears to be logging in, but then it goes back to log in screen. Then when I type my password, the password appears as WHITE dots and the computer finally logs in. Anyone has any idea what is causing this? Also, how do I avoid this double log in process?