Site not working from behind firewall

I have a WordPress 3.4 site setup on an Ubuntu VM. On my LAN it works fine, but trying to access it externally it does not respond at all.

I can redirect the port forwarding/NAT setup to my Joomla server, and that works fine, but for some reason the WordPress site does not work. This is done by only changing the internal Address Object, so I’m pretty sure that the forwarding is configured properly and working. I’m not doing any port translation.

Checking the stats in my router shows that requests are going to the internal IP, but there is no response. Apache is configured to respond to any port and server requests.

I have a internal DNS server which I’ve added my internal IP, and externally the DNS is pointing to my external IP which seems to be resolving properly (again, the Joomla site serves up correctly). So from both internal and external I’m accessing the site with the domain name (not IP addresses). The domain names are entered correctly in Settings > General.

I’ve just about given up on WordPress at this point. The install was slightly easier than Joomla, but this configuration problem has me stumped. I’ve spent hours troubleshooting, I could have set up 20 Joomla sites in the amount of time I’ve spent on this.

Hopefully someone has a suggestion that can get me back on track.

Thanks everyone for their time.