Hi Joe, I'm glad to say you that problem is solved. We don't realize that although there is an UseGoogleCDN=True configuration in web.config, we forgot that previously (in a test) we put an UseGoogleCDN=False configuration in user.config, and therefore it overrides web.config configuration (a little embarrassing mistake!). JQuery works perfect now.
It seems that the only necessary url to authorize is ajax.googleapis.com (we don't use Google Maps).
MojoPortal is great, thank you very much!
Best regards,
Leandro