I have recently installed SP1 on a Windows Server 2003 which is also a DC for a remote location. SP1 installed OK and I have not doen any additional configuration through the Server Configuration Wizard utility. However, once the SP1 was installed, I am unable to connect to any of the shared files and folders on that server (the server is a DC and file server only). I can remotely connect to it, browse through its resources and users on the local LAN are able to access its resources. I use point-to-point VPN connection between sites through Windows' Routing and Remote Access.
I'm sure that there is some kind of security tweak, but I have no idea where and what to look for.
In the mean time, I've uninstalled the SP1 and all users can now access files and folders on that server.
Any ideas are greatly appreciated.