Does the /etc/hosts file still exist?
localhost is the basic entry that even MS installations have in their hosts file. Try opening the file and seeing whats there. If there isn't a file create one and add the line
that should cure GNOME error. As far as the internet errors go are you sure the correct nameservers are inputted into your Linux box? I'm not the expert here so this post will probably result in 20 posts correcting mine, but here goes anyway!
You'll need to know the IP addresses of you DNS servers. When you have them, stick them in a file /etc/resolv.conf (I think) like this
where 126.96.36.199 is the IP of the dns server. Add as many lines like this as you like.
To get the IP addresses go to your NT box, and in command promp type "ipconfig /all" and the IP addresses should be there somewhere (I think that command was included in the NT distribution of Windows).
I really hope that's ok, and that I haven't mislead you