We have installed an SBS2008 server for a client and all is fine except accessing the Internal Website (Sharepoint) from outside of the LAN by domain-joined laptops.
If from outside you goto the https://remote.domain.net/remote address you get on the initial remote screen. From here both OWA and remote desktops work fine.
When you then try to authenicate onto the internal website (Sharepoint) it says "Internet Explorer cannot display the webpage".
Computers that are not domain members are NOT having the problem.