My 2009 rev Mac Pro was working fine last night when I decided to run the software update for 10.10.4 before bed. I woke up this morning and though I could hear the machine on, the screens were black and it wouldn't respond to any key presses. Tried rebooting a few times and though I hear the fans spin up, nothing happens. No chime, nothing on the screen, just black. I tried unplugging all peripherals, took all drives but the boot drive out of the system, reset pram, boot into safe mode... I have two different video cards, but both are showing nothing but black. I'm not sure if this is an unrelated hardware issue and a component randomly crapped out last night or if this was caused by the update. No genius bar appointments available until the weekend so I am out of comission until then. Anyone have any ideas on what the issue might be? Side note: The video cards are two Nvidia GT120s if it makes any difference. Thank you!