SBS2003 Sharepoint

Im running SBS2003 using Sharepoint. Everything internally works fine. For some reason though, when we try to acces the server from outside we have to use the IP address to make any of the secure features work. If you use the FQDN to get to the website and try to go to /remote or /exchange when you enter your credentials the page just reloads. If you get to the page with the ip everything works.