This is probably obvious and you have already tried it, but have you tried forwarding the 2300-2400 TCP and 47624 TCP and UDP (I'll have to check on these numbers)? Under the router I couldn't see any Dynaverse servers, but after forwarding just these ports, they worked fine... did not even need to set a static IP address, which seemed to be the most-confusing/easiest-to-screw-up-and-ruin-things part.
If you run a Linksys router you will probably need to trigger these ports too, which is usually in the same control panel as port forwarding for the router, and done the same way.