I just looked on their site, there is a BIOS update for a known issue with this board not detecting the right RAM when using a Semperon CPU. However I tried to flash the BIOS but would not work, used the flash utility and the BIOS from the site, but the utility reports that it is "Not Award BIOS".
yes the bios upgrade does sound simmilar to your problem. There seems to be no reference to using single sided memory chips in the manual, it is usually noted if they are problems with either single or double sided modules.
have you any double sided memory you could try, crucial seem to recomend double sided for this board. click here