my achievements are broken

i have been thinking this a few times, there are a couple on fifa that i know i have got but not popped and 2 on AC3, i did them without a guide and nothing happened so i thought i may have done it slightly wrong and went online to follow a guide, i followed the video exactly as they did it and they still didnt pop

any ideas???

Sorry mate, I don't have either of those games, It's worth checking a few sites to see if they are glitchy,

hope you get it sorted, I hate things like that!

i had a quick look but the only thing i could find was something similiar happened to someone on forza. nothing about these two games... i have played another game and an acheievement poped(tony hawks pro skater hd) then i tried AC3 again the same way the video did and nothing... so its not the xbox