Hi Francois,
I have recently had the smae problem with my 707 after reloading my pc. There is a batch file that is supposed to redirect the activation to another server but this did not work for me either.
What I had to do was go to "my information" and request a new download link afterwhich I created a manual activation text file. After downloading what I assume to be a later version of the 707 installer(1.2) I was able to activate it in a "offline" mode - Worked a treat, now I can fly my 707 in FS9 while patiently awaiting the FSX version(I am one of the few I guess who beleive CS when they say this will happen :) ). Let me know if you still have trouble although I can only assist with the 707.

Cheers
Kevin