Yosemite white-screen crash (with avatar) Recently upgraded to OSX 10.10 on a Mid 2012 MBP (13 inch) - no problem encountered.  But a few times now I've experienced a white-screen crash.  When waking from sleep the system just shows a white screen with the round user avatar picture in the middle.  Nothing I do can bring up the proper login screen except a hard reset. 
Does anyone have a solution for this?
I have experienced this - if you type in your password and press enter, it will 'unlock'. I think it's a glitch.