Thank you for responding.
I already have one 512 and two 256.
Regardless of the slot configuration I put them in, it is as if the board will only accept a maximum of 768. The mobo usage manual says nothing about using the same size in every slot. I also have heard that its generally recommended by many mobo manufaturers, I have searched the web and cannot find any specific such requirement indicated for this board. There are some settings in the bios(voltage, interlace, etc) but tinkering around in there makes me nervous. Any other ideas?