Hi,
I am currently now running my PS3 through my router with it in the DMZ and all the ports forwarded as suggested by Rhino. In addition to this I setup my connection (wireless) manually so that I could give my PS3 a static IP address. Please use this link below http to see the easiest way to set the static IP. Use the DNS settings in this thread also. ://boardsus.playstation.com/playstation/board/message?board.id=psnetwork&thread.id=282488
So when you have done this, go into your router's homepage and use the static IP address' last digit(s) to put your PS3 into the DMZ. Depending on your router, please use this link below to help you configure the port forwarding. Find your make & model of your router, and then choose Call of Duty: World at War (or any game you are having problems with). http://www.portforward.com/english/routers/port_forwarding/routerindex.htm
Once setup, turn off your PS3. Reboot your router via the homepage, or just unplug the power lead, give it a couple of minutes, plug the lead back in if necessary. Then boot your PS3, see what happens.
I can honestly say that, after a couple of weeks of having this configuration in place, it did eventually work; whether or not another factor was responsible or just coincidence it is definitely working now.
I would like to hear your feedback, or if you would like a more comprehensive explanation, then just let me know. I can show you with screen dumps or something.
Scott
Configuration: Windows Vista Internet Explorer 7.0