I have a Mac Pro 5,1 with unflashed GTX970. I have a bootcamp partition (Win 10 Pro) for gaming which has given me no problems until the latest security update. After the update, I can no longer boot into bootcamp. I tried my old 5770 card and I could get into bootcamp. Putting in my (also unflashed) nvidia 570 or 970 gives me no joy (boots back to OSX). Have contacted apple support and all they could point me towards was to reinstall bootcamp. Could anyone please help? Thank you.