In a bid to increase my gamerscore last week, I tried the Crew Expendable mission on Veteran in COD 4 in order to get the achievement with a nice 40 gamerscore. The Mission took me 1 hour which was plagued with constant death and restarting. Then, after soem work I finally managed to do the mission but i got absolutely no gamerscore. For soem reason I never got the achievement. Has this happened to anyone else? Not necessarily on this but on something else?