I haven't played the whole game through and that FPS seems low. A while back I tried a custom time demo provided by NvNews user Weeds. Supposedly it is the same demo TheTechreport runs. Results stock and overclocked are below.
Call of Duty 4
Timedemo provided by NvNews user "Weeds"
All tests 4xAA|16xAF All enabled Texture options "Extra"
Stock Speed 575|2000:
1920x = 62.9FPS
1680x = 70.9FPS
1920x = 72.1FPS
1680x = 80.0FPS
I've had zero issues with the game maxed out @ 1920x with 4xAA|16xAF on a single GTX 260. I am not sure what's going on with your FPS.