This is good, to a point. The net knows you're out there, how to get to
you, and what to look for when it gets there. That eliminates most DNS
problems, and also eliminates the gateway issue.
That puts us back to IIS. Verify that you do have default.htm and that it's
pointing to the correct 'home' subdirectory. Also, verify you are allowing
anonymous access to the web server.
If that doesn't do the trick, let me know...I'll see if I can find another
rabbit to pull out of my hat.