I have everything set up exactly How that guide is explaining. Still have the same problem. Although I know it lies somewhere in my router configuration. I've set up servers just to play on before with no problems at all. The only thing different about this setup is the router between me and my cable modem.
It's not too awful important. I just like to make my own server to mess around on, it's a good way to learn. If anyone catches anything else I overlooked though I would appreciate it