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
http://img237.imageshack.us/img237/4...ck1920xsq8.jpg
1680x = 70.9FPS
http://img55.imageshack.us/img55/119...ck1680xhx0.jpg
Overclocked 730|2600:
1920x = 72.1FPS
http://img67.imageshack.us/img67/823/cod4oc1920xlg0.jpg
1680x = 80.0FPS
http://img246.imageshack.us/img246/2...oc1680xct0.jpg
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.