Well, I've had this issue before with COD4, but some fiddling fixed the problem for the most part. I can't seem to join any games as it gives me the 'Cannot Connect to Host' error, so I figured I would post a Question since setting up my router and DMZ didn't work. Basically, using a linksys wireless-g router and my 360 is using the Microsoft wireless piece. It's starting to get rather frustrating, I appreciate any ideas/help on the issue.