Hi, I have been using an unflashed nvidia gtx 970 graphics card in my 2010 mac pro. Today, I installed the new security update without thinking and it broke the nvidia drivers that I had installed on the computer. Now the computer won't boot (since it's an unflashed card). I still have the original AMD card that came with the computer, but the drivers on the computer are still set to nvidia so the AMD card won't boot either. Does anyone have a way to fix this? I would be eternally grateful!