I'd bought a 512MB stick for my 15" 1.25 GHz Powerbook from Crucial. When I put it in, the computer would flip out. Crucial RMA'ed it, and sent me another one. Well, the second one didn't work correctly either. I called their tech support, and the guy I talked to suggested the SoDIMM be replaced with another one that was "lower density" - same size, same specs, but more and lower-density chips on it. To be honest I didn't totally understand his explanation of the potential problems occurring with the first one (something to do with crosstalk or interference, apparently on the SoDIMM itself). I just received the replacement stick, and it's working like a charm. The reason I'm posting this is because I was quite happy with their tech folks. I didn't have to wait long on the phone; they seemed to have knowledgeable people manning the phones; and they didn't automatically assume I was an idiot. Really this should be the norm, but we all know it's not - so they deserver some credit IMO. I also thought it worth posting because there've been rumors floating around regarding Apple's memory specs having changed w/o the third-party suppliers being notified. I have no idea if that's true, but I find it interesting that the SoDIMM that worked wasn't quite the "default" setup, if that makes sense.