I got a MBP 2015 and some times when I enter my login credentials, the progress bar for the loading of Yosemite gets to about half then I get a black screen with apple logo and then I have to enter my credentials again. This second login screen is different as the blurred background pic is not my chosen desktop pic but the standard yosemite desktop pic. I also noted the keyboard is set to US and not UK (I have the UK model), it's like my personal settings are not loaded. After login everything works correctly. I read somewhere the double login is because of FileVault but in my case it happens randomly, not all the time. Any clue?