Dear mzilikazi,
I found the problem: network card configuration program recognize TWO ethernet cards (eth0 and eth1): eth0 is my firewire (1394) eth1 is my ethernet card!!!
Now I set eth1 card and now it is all OK: I can access Internet.
Maybe this information is useful for notebook's users with firewire.
I apologized to you for not telling that my notebook have one firewire and one ethernet card, and that netconfig recognized two ethernet card.

Thanks a lot for your help

Edgardo