Recently my quad core 3.1 MacPro running SL stopped displaying anything on my 24" Samsung monitor. It would start up to a black screen, and just stay that way. I figured the Radeon X1900 video card inside had gone bad, so I put in an extra GTX285 I had laying around. No change. So, I pulled the drive and hooked it up to another MP and modified the system files so that it would allow screen sharing, and then restarted the troubling MacPro. Through screen sharing I could see that the computer could ID that the graphics card was an nvidia card - but that was it. No details on the monitor it was hooked up to, or what model card I was running. I shut it down, reinstalled the Radeon X1900, and started it up. Through screen sharing, I could see that the Radeon was completely recognized, and that the Samsung Syncmaster was also recognized - even though it wasn't showing anything. In the system profiler it just said "No Display Connected." (Remember this part ) So I grabbed an older Dell LCD, hooked it up to the MacPro, and the display came to life! I then unplugged from the Dell, and plugged back into the Samsung, and now it worked! But when I check the system profiler, it STILL says ""No Display Connected." So now I'm thinking the Samsung needs a kickstart? Pretty weird so far, huh? On reboots, however, the startup screen worked fine with the Radeon. From a cold start, it would stay black and then come to life after the computer had completed its startup routine. So next I tested the GTX. I put it into another 2008 MacPro, and it worked perfectly. So the GTX is fine. I take a chance and put it back into the troublesome MacPro, and I'm back to square 1. No display response - from either the Samsung or the Dell, and the System Profile just shows an nvidia card with little detail. And, yes, I'm hooking up both power wires to the GTX as well - though I haven't run a voltage meter on them to see if their both working. So, because the GTX still won't work, I put the Radeon back in, and nothing. I have to go through the same process of hooking it up to the little Dell 14" before I get a picture, and then "hot swap" it to the Samsung 24" before I can get a picture on the Samsung. Does this sound like a slowly frying MB? I hate to loose a MacPro like this - and granted, I should be happy the Radeon's working on it again. But I am completely baffled. Thanks in advance for any comments or hints to try.