Hey guys

ive read much about this problem on blogs and whatnot myself as I have had the same problem. I talked to the manufacturer of my router (belkin :N router) and after talking to them everything was working fine. heres what they said;
log into 192.168.2.1 (put this number into a internet explorer/firefox etc address bar) or whatever the router's IP address is (not the IP address of your computer!). Im on a mac and i found the router's IP in system pref's, network; advanced button, TCP/IP tab--> it'll list the "router" IP.
find your network name and rename your wireless network. (to anything it doesnt matter) make sure you remember your password if you have one
your internet should go out b/c your connected to the old name so now you have to connect to the new one. do so through network settings or however it is on whatever kind of computer you have
connect to the internet under your newly named network, make sure you can connect to the internet
once you do, try to connect the ps3 to this network. I just did 'easy', scanned for the network, found it, put my password in and everything came out fine. i can finally play COD again

what happened before and what i imagine the problem is for just about everyone is that there is a conflict of IP addresses between the computers and the ps3. renaming the network is like rebooting your router and it will then assign IP's to all the different computers or devices that request it.
I had a DHCP set up with a dynamic connection set up which should have automatically assigned IP's to whatever device that tries to connect to the network(with the right password) but it wouldnt work. But after changing the name and restarting everything, im good to go now.

hope this helps