Co-op hosting problem...

My problem is that I can host an online game in co-op, but nobody ever joins. It appears as though people don't even see my server. Moreover, when I search for servers, there usually aren't displayed more than 8 servers. What the hell is wrong? I do have a router. I tried port forwarding. I set my dynamic IP address to static IP address and port forwared some ports (appearently) needed for CoD WaW. Nothing helped :/

Does anyone know a fix for it? I'd really appreciate it.

Thank you in advance.