Re: DXDiag incorrect memory?
Check with some other tools, like GPU-Z. If it happens there, too, maybe some RAM went defective, I don't know.
Otherwise, it's probably just a Windows bug. A weird one, though.
Overdrive PC Core2.SLI:
Core 2 Duo E6600 @ ~3.5GHz,4GB of DDR2-770, 8800GTS 640MB @ 621/1836, Western Digital 640GB, LITE-ON 20X, CM Stacker 830, Enermax 620W, Vista Ultimate 64-bit
3DMark '06: 10,302
SuperPI 1M: 15.194s