I've got a MacBook Pro Core-Duo 2.16Ghz. I had two sticks of 1GB ram, and I wanted to pull one out and add a 2GB stick, for a total of 3GB. When I do this, the computer doesn't work...no startup chime, blank screen. If I put in one of the 2GB sticks by itself, or one of the 1GB sticks by itself, it works...so it's not bad memory. I know it sounds like I probably just answered my own question, but I could swear I've heard of other people on these boards doing something similar. Can this model really not support higher than 2GB?