Same problem here. Have you already solved this problem? Please do email me at email@example.com or firstname.lastname@example.org
I am sorry, it's been a while and I don't remember all the details.
But essentially I believe it was the THIRD motherboard that the PC store sent me under RMA that finally worked - it first posted with the cheap RAM, then I changed the voltage in the BIOS and was able to install and use the high-end RAM.
I have never had any problems with this machine ever again, since these initial troubles. I am very happy with this blazingly fast beast.
So I think the quality control at ASUS has gone the way of the Dodo bird.
Hope this helps,