All right, prepare yourselves for a rather long story. Serious answers only, please; read the whole question.

I have a cable modem connection with a D-Link router DI-634M. So I have the router box, and the modem box. Internet works fine for me, and I can host a dedicated Tribes 2 server just fine with this computer, but NOT any warcraft 3 frozen throne custom games.

Now, what I have done about the problem: I have searched through countless forums, gone to portforward.com and followed their instructions. My router has ports from 6112 to 6119 opened, both TCP and UDP, allow always. My windows firewall is off. I have a static IP address and all that good stuff.

Now, am I forgetting something?

Okay, I figured it out; this is something No one ever mentions. Okay, let me help the rest of you: you have your router ports forwarded, right? Okay, your computer firewall is set to allow it. Your router firewall is set to allow it. Well, holy !@#$, your MODEM has a router too. And accessing the router hub is not as easy as an ip address: for instance, mine is http://gateway.2wire.net/xslt . I don't know if you can find it in your manual, or if you can Google your modem brand/model.. you may just have to ask your isp. Anyway, this fixed it and I can host as normal. Woot!