Remote Desktop Client access issues

My Windows XP computer is not accessible from an XP computer outside the LAN using the Remote Desktop Client (RDC). It was working when I set it up the first time. Nothing changed as far as I can tell.

It is accessible from a computer on the LAN accessing it on the same subnet using private IP addresses. I can also access it from a computer on the LAN and typing our outside static IP address and the RDC port#. We have a DSL router with a built-in packet filtering firewall but we have enabled port forwarding.

The question is why does it work for a local computer going out to the Internet and back but not from a remote system?

Thanks in advance, Guy…