I have a boot issue that defies all explanation or any of the standard approaches of resolution. I feel like I have tried everything and from what I can tell (with the exception of safe mode which doesn't work either) the machine seems fine- it just won't boot. I typically will spin the spinner forever and if I wait long enough it reboots. It started when had to restart my mini with Mavericks 10.9.5 and after normal operation whilst in screnn saver it sounded like it chomping CPU as the fan was and when I tried to force quit whatever it was it didn't do anything. The screen was black with the rainbow spinner. It was just spinning forever on some bad app and after that I rebooted but it never came back. The odd thing is I have tried all of the usual approaches and nothing fixes it. When I start up normal, after I enter the disk vault password, it just get the spinner forever, or eventually it will randomly reboot and start over. I unplugged everything but the keyboard and I started in recovery mode and tested my disks but they both were fine after I unlocked them. They verified and there were no errors whatsoever. Then I started in diagnostic mode and did a full test and it came back clean even after an exhaustive test. Nothing was up in hardware. I tried safe mode but when it starts it asks me for my disk credentials per usual and then I see the thermometer bar for until about a quarter of the way through and then the bar goes away and I just get the apple logo - no spinner - so it was worse than when I started normally. I also notice attempting normal boot the monitor brightness changes a lot while the spinner just spins endlessly. It's almost blinky, though after my umteenth try this behavior has subsuded. I have a lot of data and prefer not to do a time machine restore because 1.5 TB will take forever to restore, but it seems like my only option at this point, assuming it even works. One other thing is when I plug the power cable in it chimes immediately. I don't have to hit the power button. Resetting the VRAM does nothing either. Is there anything lose I might try before trying a full restore, something I'd like to avoid since Time Capsule seems so unreliable? Maybe some other key combo that gets it into some other mode that I don't know about? This is really a weird one.