I administer six SBS2003 networks. Three of these have additional Terminal Servers on the domain. My usual way of configuring things is to use ISA Server to publish the Terminal Server RDP on port 3389, whilst publsihing the SBS Server RDP on port 63389 for administrative purposes.
I have an occasional problem on the three neteworks with Terminal Servers. I find that I cannot externally use RDP to log into the SBS Server on port 63389. However, when this happens, I can still log into the Terminal Server on port 3389. I have noted that at this time I can never RDP into the SBS Server from the Terminal Server. My only recourse is, from the Terminal Server Command prompt, to reboot the SBS Server using Shutdown.exe /m \\server /f /r. When the SBS Server has rebooted, everything is ok again for a few weeks.
So why does this happen just on the networks with Terminal Servers. I have properly joined the Terminal Servers to the Domain by using the steps outline in ADS_TermServ.doc