ASUS M2N-SLI DELUXE and XFX 275 graphics card conflict

I built my system from the ground up and originally running a GTX 8600 graphics card. Thant set up ran for a year with no issues or crashes. 3 months ago I updated to a XFX 260 black edition card and have had nothing but problems. I had to send the card back 2x and finally XFX sent a XFX 275 card and still having the same problems. The issue is when you are playing video games ie; GTA 5, Crysis, Call of Duty 4 or any other game that used a lot graphics power my system freezes or just completely shuts down and restarts. This happens with no blue screen and completely unexpected. I am monitoring CPU temps and have the fan on the card running at 100%. Every thing is running cool and within the guidelines. I have all the new drivers installed. I also have tried to run at reduced settings on the graphics card. Does anyone know about an issue with this mobo and the 260 series cards? Also if I go back to my old card the pc works fine and no issues.