I did some research on the Internet and found that the Hynix RAM modules were even original built by Apple, and it therefore will not be returned. When changing the memory module I have seen that really put a 512MB module from Hynix in it. The replacement is easy, you only need a very, very small Phillips screwdriver (and otherwise follows the video tutorial that can be found on the web).
The store was immediately recognized and it works perfectly: So is the few Euros worth at any time!
