I'm a noob (or is it newb?) to this game, just started the campaign a few days ago but loving it. Gonna give lots of deets about my issue so that all the information is out there.
First of all, I keep my gamertag and game saves on a USB drive since I play regularaly on Xbox's at 2 different locations. Last night I completed the mission called "Zero Dark Thirty" on Normal difficulty and when the next mission was loading, the achievement ("Save Me Some Cheerleaders") didn't pop like it normally does. I thought this was weird and hit the Xbox menu button to check my achievement progress, and it said my gamerscore was 0 (it's actually over 26,000). I exited the game then restarted it, and after ensuring my profile was properly logged in and my actual gamerscore was once again displayed, I replayed the entire mission from the beginning. Again, at the conclusion of the mission, the achievement didn't pop, although the game registered the completion and recognized the M-COM stations that I had found. Next, I turned the console off, restarted it from scratch and played through the same mission on Easy difficulty, but once again, no achievement even though, when looking in the "My Campaign" menu, it shows that I've completed this mission on both Easy and Normal.
Any idea what the problem could be? I was reluctant to play through another mission and see if the achievement would pop in case it would prevent me from getting that one as well. Thanks in advance and hope the explanation wasn't too long.