Hey i have the same problem! I have a similar setup as you, same mobo and cpu, except my psu is a seasonic x650 but it did not help solve the problem. I tried booting with the support software CD that came with the mobo but for some reason the menu from the support software doesn't show up. I tried booting window 7 through a DVD+R disk but that doesn't work either. So now im in the same boat as you i guess..
Try boothing from a disk if your USB doesn't work.
Try boothing from a disk if your USB doesn't work.