Bought a 2008 3.2 GHz dual core Mac Pro, that came with an NVIDIA GeForce 8800 GT graphics card, and I upgraded that to a GT 120 card. I've been using an LED Viewsonic monitor with it since buying it, and everything had been going fine up until this morning. Last night I had been using Vista and doing some high-res gaming, and no problems until today. Now when I try booting up in OS X, it doesn't get quite past the Apple icon before black wipes down the screen, so nothing gets displayed. I've tried every single combination I can think of (except buying a DVI-Displayport adapter). I've tried different monitors with the GT 120, and they work. I've tried reverting to the old 8800 and trying out different DVI ports, and still nothing with just the Viewsonic. When I dual-monitor, the Mac can detect both monitors plugged in, but nothing gets displayed. What I haven't tried yet is using it with another Mac, but then again I don't exactly have another Mac to test it on. The funny thing is that the Viewsonic had been working perfectly up until this point. Could it be that intense gaming burned out my monitor? That might not be the case since it can still be used in Vista. Should I call up whoever I bought the monitor from and ask them for a replacement, or is there some sort of fix?