I've been having this problem all day, anyone else?

I =DID= for the 1st time today plug in a wired ethernet connection to the unit, but every other game works, including PSN and downloading... any ideas what the problem is?

It may be that ports used by the game aren't open. I don't know which ports the game uses though. You could also try enabling UPnP if you haven't already.

What I did though, was just set up the PS3 as a DMZ so all ports would be open. You have to have your computers set up with static IP addresses though.

This is not safe at all for a computer, but I don't think it's a problem for the PS3 because of the closed nature of the system.

well, interesting development... 4 days ago my router "died", ie: no power. Verizon Fios sent me another which arrived today, and voila, COD4 works just fine again. While the PSN and other PS3 games worked just fine throughout the last month, perhaps COD4's servers are just a bit more sensitive, and the fact that my router was on it's last dying breath was being felt?