I have a Powerbook G4 that I wanted to upgrade to 1.5G from 512MB. So I added Corsair 1GB DDR RAM to the notebook and it seems to have issues recognizing both at the the same time. When I put both of them in together, it never seems to recognize the bottom slot. Putting in the 512MB in the bottom w/o the 1GB the Powerbook boots up fine. Putting in the 1GB by itself and it gives beeping noises on bootup, but it'll boot up if I put it on the top slot. Any ideas what the problem is?