I just tried to boot at 8x400 with 2.40A and 960Mhz with my G.Skill 6400 2x1GB (4,4,3,5) and i got a total power down.

(Unresponsive power button)
I had to unplug the
psu wait a few seconds and reset the
cmos in order to boot again.
Got scared after that and went back to 9x330 2.50A 825Hz (4,4,3,5) which i am right now. I want to try again but this power down thing is really fustrating, i am hoping it will not happen again.
I really wonder what are the causes of that.
GA-X38-DQ6, F5g. Q6000 G0. Vcore 1.31