Chances are you have bulletproof setup correctly, but you are not forwarding port 21 (or whatever port you are using) to your local PC. This is a great website that has direction and even screenshots of how to do this on most commercial routers. http://www.portforward.com/english/r...outerindex.htm
Also, depending on your router setup, your LAN (local) IP address will change every time you boot your laptop. Most routers have a "lease" time on your local IP, so if you reconnect within a certain period of time it will reassign the same local IP. If you find your internal IP keeps changing, you might want to think about making it static. http://www.portforward.com/networking/static-xp.htm
You might want to think about setting up a dynamic domain name. This way you don't have to remember your WAN ip address, and the domain name will update if your WAN ip ever changes.
(This is free for personal use). http://www.dyndns.com/