probably what you have done is overclock the motherboard (by increasing the FSB, which is the standard way to overclock a system). The effect of overclocking the motherboard is to increase the speed of every component running off the motherboard, that includes the cpu and the ram. the problem is that the ram cannot go very much faster before it craps out. To compensate, the ram should be 'underclocked'. This can be done by changing a setting in the bios to make the ram go slower.