I have the same setup. I am using Crucial Ballistix DDR2800 RAM, and having issues with standby/rebooting. The machine doesn't rePOST and hanges in La La Land until I hit the reset button enough times to make it POST properly. I had this problem with the first mobo. I returned it for a replacement and had the same problem. I thought I solved it with some BIOS settings, but it's returned and is happening every single time the computer restarts, resumes from standby, and sometimes on a cold boot.
Have you had any troubles like that? What kind of RAM are you using?