My MacBook Pro fails to start. I hear the "ding" sound, the keyboard lights up, but the screen stays black.
After a couple of minutes, I hear the fans growing louder, until after a few minutes, the computer stops.
I tried a few times, also closing the lid, plugging to a TV, options key, etc. Nothing.
Except, once in a while, it seems to start correctly, the screen turns on, and then it tells me I have forgotten my password and offers to reset it.
There is no option to say "NO I haven't forgotten".
When I play along and reset my password, at the end of the process it says my password was successfully reset (including something about FireVault), then it requires me to restart the computer to complete.
Of course, once I restart, I'm back to square one with the black screen. I've managed to reproduce the reset screen 3 times so far - without really coming up with a rule as to when it happens. The rest of the time, just black screen.
It's a MacBook Pro 15" from 2011 (I think), running Yosemite.