It can happen you get an error when you want to play one of the new Multiplayer Maps of CoD4.
If the error says 'mapname'.ff is different from the server or any other error with a mapname you can try to use an other set of the orginal mapfiles.
Choose the link with the map that gives an error. Download the zip.file and use the 2 .ff files to replace the ones you have now in your |zone| folder in the CoD4 folder.
And hopefully this works and you don't have to re-install CoD4 and download 1.6 patch again.