Just out of curiosity, do you have an Asus mobo? and if you do, do you have the EPU-4 engine running in background? Every time I reboot my PC it defaults to max power saving mode and I get the same lag as you described. I have win 7 pro 64 bit with a HD 5770 and it took me a while to find the problem. Hope this helps

No, its an MSI P55-GD55 (I meant to buy the 65 but grabbed the wrong box at Fry's and said f*** it, lol). From what I can tell, I think its a PB/64bit OS issue. Probably specific to Windows, because I also run CoD4 under a 64bit MacOS from time to time and never had this issue.

For me and most others I've talked to, the issue quiets down after a minute or two into the map. And once you've joined a server it doesn't do it as bad at the start of each map, though it still does it a little bit. I don't compete, so for me being a little laggy in the first round isn't a huge deal. For someone more serious about the game it would probably be a major issue though.

im running cod4 perfectly on windows 7 64, could it be something in your config?