have a read of the stickies in the OC forum
you want to set your RAM to its rated voltage and leave it, there'll be a sticker on the side, 2V I think from quick google
if raising your CPU voltage isnt helping then try your NB
But remember as you raise your FSB that also OC's your RAM as well as your CPU, so you need to lower the divider to ensure its not the RAM holding you back, as I said have a read of the stickies, they should help you