i dont have the same board, i have a ASROCK K7S8X, are there any dip switches/jumpers that need setting on the motherboard to enable 400mhz FSB, also check that the clear cmos jumper is not set to clear.
could you try the motherboard at 333mhz instead to check if it works at that.
unlikely with crucial memory but sometimes the memory can be unhappy at 400 FSB
take a good look at the manual and double check any jumper settings.
if the mobo doesnt appear to post (no beeps etc.) check the light on the mobo is on as that rules out power problems.
are you sure you have connected all the case connectors properly, if in doubt remove all except "pwr sw" and try again