This might be more a technical problem than a problem related to the game, but one of my achievements has managed to unlock and not unlock at the same time.
After finishing my 30th game, I didn't get an achievement pop-up. So I checked my achievements and it still said I had 9/12 achievements for 140G (still needing the Tours of Duty and the Best Squad on all maps). However, when I clicked on the game, sitting there at the very end of the achievement list was the unlocked achievement for 30 games played, gamerscore, unlock date and everything. At the bottom of this screen it says 10 of 12 unlocked. The achievement hasn't counted though, my score hasn't increased, and I've tried everything I can think of to get it to re-unlock, but it just won't. The reason it has glitched is because my hard drive had completely maxed out at the time, and apparently there wasn't any more room left for me to unlock achievements. I never knew you needed hard drive space to unlock achievements.
Any solutions or suggestions would be much appreciated