Yes, Baldaccar, posts diasspear when Apple finds information leading to fixes they do not approve of. The problem here is that Apple's original support, geniuses, Authorized Reserllers, you name them, whenever they change a motherborad they apparently forget to set the S/N on the new mother board.
Apple's solution, probably, I am just guessing, is that you go again at the Apple Authorised Dealer and ask them to fix the problem. I have also discovered that there is no "legal" way of getting hold of the famous Mother Board Serializer which, I think, is a software supposed to be used only by Apple's authorised repair centres and can be downloaded only from Torrent sites (anyone knows of a good link)?
The moreale is: this is Apple, take it or leavet. For people willing to tinker with their hardware and software there's Linux and other OSs. Apple's is a walled garden, where you can do only what the master says, no matter how wrong s/he could be.
Cheers
Andrea