I wanted your modem model, not router model (I wouldn't assume your router also served as a modem), but the addition of "Revision C" helps me a bit. You may want to view this site in case you haven't already. The FAQ on Gaming Mode might be useful.

I'm still not ruling out DMZ as a possible solution since I still believe it should've worked. Next time you try it, make 100% sure you're using your computer's IP address.