It seems your problem is solved and you can now access your ubuntu servers default web pages from the outside world so my advice would not be necessary.
I use nginx and it's sites-enabled/100-mysite.vhost listen directive is "listen *:80;" so it's listening on my 127.0.0.1 and 192.168.xx.xx IPs by default. From the inside of my LAN I have no problem bringing up a page for the domainname associated with the EXTERNAL IP of my router, but I am using a DMZ from the router to my internal server.
What I did have a problem with is using this server as a DNS slave and for the life of me it would not transfer the /etc/bind/slave records and I think it finally worked after this tweak which means I may not have disabled apparmor on this Ubuntu raring server.
~ cat /etc/apparmor.d/local/usr.sbin.named
# Site-specific additions and overrides for usr.sbin.named.
# For more details, please see /etc/apparmor.d/local/README.