I think your router is blocking PS2 incoming connections. Go to your browser and type in 192.168.1.1. Then you should be prompted to type in a username and password. By default both password and username are admin. Click on the advanced tab. Go to firewall and disable it. Try connecting with your PS2 now. If that doesn't work then go back onto the Dlink page (192.168.1.1) and try to enable UPnP. I don't have a dlink so I don't know how to do this. If that still doesn't work, then follow this link and open the correct ports, read everything on this page:
http://portforward.com/english/route...on_Network.htm . Finally, if this doesn't work either, you will have to put your PS2 into a DMZ. Which can be found in the advanced tab on the side. However, DMZ is a last step.