and the reason is very simple:
your FAA licence is based on a licence, that no longer exists! it has nothing to do with 9/11 but with the fact that we now have JAR and your licence has a new number! It's a completey NEW licence!
I'm an American citizen and my old FAA, based on my old German one, is also no longer valid. I, too, must apply for a new validation at least 60 days before going to the US! I went to the States last January thinking, since my (old) FAA licence is in their system, I'd have no problem and the 60-day deal was only for new ones... I was wrong
Westy