Hey Everyone,
I recently purchased a 2009 Mac Pro and upgraded it to 5,1 firmware and Sierra 10.12.6. For the sake of those who find specs helpful in isolating the problem, it's the 2.66Ghz 8-core, 24GB RAM, Booting from an OWC SSD drive in a PCIe slot. I also put in it a Nvidia GTX 960...