I'm leaving this as an answer but I don't want you to accept unless we figure it out. I will continue to work with you further until its working.
The ports closed. Tested it here (port tester, and remote desktop).
You can confirm yourself here:http://www.yougetsignal.com/tools/open-ports/
I personally run a network with 6 servers running 2003 right now, all of which use different ports (you can manually set the port you want remote desktop to use). None of which require anything fancy short of that simple port forward. The problem is likely the router's port being forward, or the actual external IP address. If you have a static IP address, or a block, let me know. If you have a dynamic address it could have changed on you (there are ways around this too).
Start with the simple tests, I'm sure you have, but its best to double check. Log into the router, be sure the external IP address in the status is what you gave me. Also confirm the port is forwarded from the external interface to the internal IP of the server, and if the "rule" requires a checkbox to do so.
Based on your responses I'll try not to bore you with the basics, but we need to narrow it down. Also not to miss your previous question, no Ident is not required.
Now, if you've done all this and its still not working? Try this. Use a different port in the router to forward (nothing that's being used please, try something high like 4500). Forward it to the default 3389 internal IP.
Test the remote desktop externally using the site I provided, or by remote desktop doing the IP address like this (just as an example, you will fill in your the external) 192 68 10 10:4500
The colon will let it know to use a different port, the router will still forward it to 3389 though w here the server is listening. If the : doesn't work, try it with a space, but I'm near positive its a :
Edited by jnayes on 9/16/2010 at 9:12 PM EST