Early 2013 MBPr 15 running 10.10 PB 6 ( hadn't had time to update). I was in mail.app and saw the pinwheel but system was non responsive. Tried a reboot and I saw the screen below followed by a message saying to problem restarting press any key and cycle repeats. I checked the disk and no errors reported. Tried PRAM and now I still see the screen below but I hear the on sound and cycle repeats. I am still not ruling out HD failure as my Mac Mini showed no errors in DU but still was defective and needed to be replaced. Failed HD or other issue?