I have Corsair XMS3 and I can't disable NUMA either.
I think everybody that did disable NUMA has other brands of RAM.
I noticed in my x58 mobo that my E5640 didn't want to boot with the Corsair RAM. I think I might try a different brand.
After being inspired and tutored by you chaps on this thread, I couldn't resist building a couple of SR-2 rigs.
I don't think it's a brand issue as both are running with Corsair RAM and NUMA disabled. One has bog standard XMS 1600 and the other XMS Classic 2000MHz.