Recently I've started playing The Saboteur, and I've unlocked around 15 achievements for it so far. However, only 10 or 12 show up as unlocked.

It doesn't happen every time, but what happens is I will unlock an achievement, press the guide button to view it, and then it will say I have 0 achievements for the game. I then sign out and sign back in to see if it fixes the problem, and my achievement list shows that it was never unlocked. If I then try to get the achievement again, for example "Kill 50 Nazi guards with stealth", I can't unlock it. I guess the game thinks it's already been unlocked, because I can view my stealth kills through the stats menu, and it is in the 70's, which is clearly enough for the achievement. It has happened on other story related cheevos too.

I've never had this problem before, and I'm trying to figure out if it only happens on this game, or if it happens on other games too.

Help would be appreciated.