This mic thing has been really frustrating, but I just did something that finally worked for me. I can't believe I didn't think of this sooner.
I had tried setting up the ports but that never worked. I could never talk or hear. So I was playing with the cable from my PS2 plugged directly into the cable modem. I could talk & hear fine but you can't get on the net cause the router is not plugged in.
I realized that I had an extra switch lying around so I used that. I now have the Linksys 10/100 Workgroup switch plugged in between the cable modem and my Linksys Wireless router. One cable comes off the switch and plugs into my PS2. Another comes off the switch and plugs into my router, which allows me to use my home wireless network and the PS2 at the same time w/o having to deal with opening up ports to play. The switch is about $40-$50 but I'd say it's worth it to not have the headache.
Amazon.com: Linksys EZXS88W EtherFast 10/100 8-Port Workgroup Switch: Electronics
Just remember that anything plugged in the switch does NOT have a firewall to protect it. For your PS2, it's fine but not a laptop or desktop. Later.