RRAS Server 2003 Problem

I can't get VPN clients to even see the VPN server to log in. I just set up
Windows 2003 server. They get an error 800, which essentially means they
are not connecting. I know, however, that the router is set up correctly.

I am getting a 20106 remoteaccess error in my System Event Viewer log when
RRAS tries to start. That error message says the following:

Unable to add the interface {58FD737A-011A-4406-A557-8B2B36D6E141} with the
Router Manager for the IP protocol. The following error occurred: Cannot
complete this function. There is only one mention of this in the
knowledge-base, which does not address this issue, and the TechNet site
gives one little burp about my network adapter not being dedicated.

I only have one network adapter in the server. Do I need another one
dedicated to RRAS? Is that a requirement or just a best practice? Any
guidance on any thoughts you may have will be appreciated.

I want people to be able to work from home via their DSL/cable connections.
Dial-up is not needed.