I acquired a Mac Pro from somebody which I THINK was a 2008 model. I initially had a black screen, after unplugging it and leaving it for a while. I decided to try it again with a different monitor and it worked fine. I moved it once again and now I get no video again! It was working fine, I don't understand what could be wrong that just changing monitors would do this? I have continued to try it with different monitors and cords and nothing seems to fix the problem. I would buy a new graphics card but I have no way of knowing that that will actually fix the problem and they generally start at about $100.