I've installed a GTX570 in my 2006 Mac Pro. It works great in Boot Camp, much better than I expected in fact. On the Mac side, I am running 10.7.2. I installed (prior to switching the cards out) ATY_Init from here, and the graphics driver bundle from here. I've got a helper card en route from MacVidCards, but I thought I should at least be able to boot into the OS without it. However, the system boots Ok, I can ssh into it no problem, but the displays are blank. Can anyone offer any advice on this, or do I need to wait for the helper card to arrive?