Cannot do video conferencing with AOL IM

I'm running Windows XP. The camera and software installed fine. When I bring up the camera thru the control panel, the image displayed is great. Here's the problem. When I try to do live video with a messenger program such as AOL IM or MS Messenger, I can see myself in the lower left corner and my brother can see himself on his computer but neither of us can see each other. He doesn't have the problem with anyone else so I have to believe it's me. When I try to establish a video connection with him and he accepts, several seconds later I get an error message that says the connection cannot be made and there may be a firewall problem. I've disabled the router firewall, the Macafee firewall (it comes with Comcast, the ISP) and the Windows XP firewall. I still get the same error message. Any thoughts or suggestions on the problem?