OWA only shows a series of RED Xs externally, but works fine in LAN?

[toksoladuti]

We have a new install of Windows 2003 SBS server, with Exchange 2003. OWA works fine when connecting inside our LAN, however, when anyone log in externally, they get the login in prompt and that works fine, but in OWA all of the icons on the left side and top of the screen are blank placecards with Red Xs. All the settings on the server are the defaults, and on our Watchguard firewall ports 80 and 443 point to our server. What do I need to check/change. Thank you.