FYI for those who have gamers like Xbox and have VP and is having trouble connecting Xbox online. With Dlink DI-604 router involved, I recommend ya all upgrade the router firmware. The latest firmware is June 2006, not sure the day, but you should be able to recongize on www.dllink.com website.
I found out about this today, that firmware was intended to solve the port forward issues with Xbox and VP, understanding old firmware with DMZ enable, they would take over whole port and push out Xbox port requirement. But with newer firmware, DMZ would take over what is really needed leaving the rest for other devices.