Acer ram problem (won't work with 4gB sticks)

Hi all have had another problem re upgrading my Acer 7720G from 2Gb to 4Gb! I replaced the old sticks with 2x2Gb from crucial and of course I got the BSOD and no way of getting it to boot. Since then I replaced one of the old sticks which gave me 3Gb and it worked for a few days, now I get fragmented sounds when I boot and the mouse has become very erratic and sticky!! SO I have replaced the original 2x1Gb sticks and am back to normal BUT I would like to know how can I get this to work with the 2x2Gb sticks as I have been lead to believe that if I upgrade to Vista 64 bit they will work fine? Acer told me to flash the bios but I am loathe to do that as it's only 8 months old, so please any kind people out there with any idea's what I can do, I appreciate you looking at this thread as I know how many people have really serious problems on here, thanks one and all, Ken.