I have tried to upgrade my E1505 from two 512mb RAM chips to two 1gig chips and the computer doesn't boot up. I have re-seated them several times, but it doesn't boot. If I place the old 512 chips back in, it is fine. I did upgrade the BIOS (now A15), and I don't know what to do now. Any suggestions? New chips are PC2-6400S-666