I have the above board and had 2X1 gig running in dual channel . I than bought 2X1gig of same spec but different batch memory. If I have slots 123, 124, 234 filled system is fine and boots into windows, though with 124 filled windows only sees 1Gig. With all 4 slots filled, PC turns on but there is not spash screen or anything else.

Some one suggested increasing the northbridge voltage but could not find it.
I have manually reduced the speed from 400MHZ to 333 but still no joy.