I keep running into errors where my display driver crashes. I have my larger monitor connected to my GTX 560 Ti, and my second monitor runs from the built-in graphics. I'm not sure what causes the error, because it is not consistent at all. Sometimes it happens when I am playing games, sometimes when I am chatting on Facebook, and sometimes when I am not even at the computer at all. I am not currently overclocking the card. I was at first, but I stopped because of the error. That did not seem to help at all.
It also does not appear to be an overheating issue. I monitor the temperature of my processor and my GPU. I do notice that after the error, my Core Temp application errors out and shows all of my cores running at 98 degrees. But when I open the application, they show in yellow and have a ? beside them (indicating maybe the software isn't able to record the temperatures).
I'm wondering if it may be a PSU issue. I felt like my PSU would be enough to run my system, but so far I haven't been able to continually run my overclock at speeds that others are getting, and I continue to have these issues with my card.
How about you try to connect the second display to the second DVI/HDMI port on your 560Ti? It could be a PSU issue, but getting 98 degree on your cores is something not safe, at all! You have a good build, I would try to use another GPU, maybe an old GPU lying around, just to be sure its not a faulty PCIe itself. I have had an issue with a faulty PCIe where the GPU readings like temps, fan RPM would not show up, so that can be start.
I have Gygabyte GTX 560 TI also and have been able to fix it. It's stable with NVIDIA 290.53 but I've also installed EVGA Precision to change a few settings and control the fan. Core Clock = 822, Shader Clock = 1644, Memory Clock = 1900, I keep fan at 85 for MW3 and BF3.