kowa, honestly I believe this is an issue with the Asus X38 boards. I had a P5E3 Deluxe with the same 1800 C7 Corsair ram. It would boot at 1333 but no higher, no matter what timings or voltages I used. I knew the ram was good because I had used it on a P5K3, so I traded the P5E3 board for a Maximus Extreme. The Corsair runs fine for me on this one, but I have seen at least 3-4 other reports around the web (besides mine and yours) of folks having boot issues with Corsair 1800 C7 + Asus X38.