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You may want to look into Crucial.com for RAM. I've seen a lot of people recommend it. Including myself.

I bought RAM from a discount site, don't remember which one, but it wasn't memoryc and it made my PowerBook crash. I bought from Crucial and it's worked great for my PowerBook and also my girlfriend iBook.
 
if you go to newegg.com, you can see reviews on ram chips to see if people have used them with MBPs and if they worked
 
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