I'm trying to add ram to my PB G4 15" 1.67 SLSD. I have a stick of 1GB PC 2700 CL 2.5 which is not recognized in either slot. I have 2x 512MB which work fine. Is it the CL 2.5 which is the problem? I didn't try the 2.5 alone in the PB. Is this a firmware issue? Thanks.