I purchased the PYN GTX 570 off of eBay to use as an OS X update-card/back-up to my current GTX 780 Ti Classified in my 5,1 Mac Pro running Mavericks 10.9.2 with the Nvidia drivers prior to the most recent OS X security update. When I remove the GTX 780 and put the 570 in and boot the computer the screens stay black continuously, even long after the computer has fully booted and should be showing me the desktop. Before I go through the hassle of trying to return this card I just want to make sure I am not in the wrong anywhere. I know the Mac OS X drivers support the 570 natively now, but the current Nvidia drivers should not affect the GTX 570 either, should it? Any help would be greatly appreciated.