So I have an Intel Mac Pro, 12gb ram, 2 x dual core Xeon. 250gb SSD, 3TB Sata Drive. GTX 560 graphics card. Lion 10.7.5.. It was working fine then I updated to 10.7.5 and then the mac wouldn't boot. j I turned it on, it chimed.. but screen never came on.. no logo, no white screen, no grey screen.. just no screen at all, blackness. The monitor is working fine with other computers and the graphics card was working perfectly before I updated. I have tried resetting PRAM and SMC, Tried Safe-booting, Tried booting off another drive and booting of an install boot disk. Nothing I do works.