Hello John,
My problem is not solved yet although I tried several things. I don't know if you have access to the TSB forum in the Renn Tech Org but there I found an interesting and updated TSB about this subject (
http://www.renntech.org/forums/index.php?act=Downloads&do=downloadv&id=647)
This TSB tells you that the remote control may learn away from the central door locking / anti-theft computer just by changing the battery of the remote control !! It is described how you can try to learn it again to the computer.(I tried this latter option but it didn't work).
About my particular cas, in the meanwhile Porsche Belgium agreed (after a hard but polite discussion and after threatening with a court case, - can you imagine for such a problem !)- that they will pay for a replacement remote control since I have a Porsche second hand car warranty.
I still have to make an appointment now with the workshop which will be done in a few weeks. I will let you know the outcome (because I am not even sure that the remote control is really defective, it might have learned away from the anti-theft computer...)
Best Boxster regards,
Alfred