Another aMSN thread (possible firewall trouble?)

Hey everyone. So today I finally broke down and downloaded aMSN for my Intel iMac. I heard from other members that you can use the iSight (in my case, the built in one) with PC users using MSN Messneger. I couldn't get this to work.

I attempted to do this with a friend who is using the newest version of MSN Messenger (at least, I believe so). At first I invited him into the Webcam chat. He said that it was loading...eventually it timed out. So he invited me, before I even had the chance to say "Accept or Decline" in his window it said I had instantly declined it. So I couldn't even accept it to begin with.

I went to their FAQ and it said something about "possible Firewall, problem not yet fixed, is being worked on." So I flipped around the windows in the actual aMSN messenger client and got to webcam and it comes up with a box saying "You are firewalled or behind a router" in red letters.

I really just want to get this over with and know that I have the abilty to use the iSight with MSN users. I've been hearing this problem for months since before I got my iMac and hoped that I could download a program and just go around it....Mecury Messenger is horrible for webcams and takes a picture about once everyone one second (plus the screen is completely blue overtoned) and I have heard bad reviews with Adium.

The sounds of it make it sound like it's some firewall...I know nothing about firewalls other than when I had a PC they normally kept me from doing a lot of things, I don't know how to turn them on or off (if that's possible) or anything!