This just started doing this yesterday too.. when even i go to look at my achievements through the dashboard i can look at my games but as soon as i get about 8-9 games down the way i'll see a game with the loading circle and when i move to that game it stops loading and all of the achievements disappear. i'll still have the scores for the games and my complete gamer score intact but i can't view any of the achievements for any game. even more is that when i press the home button to look at them it says my gamer score is zero and i can't look at them.
the only way that seems to fix this is by signing in and out of my profile.
just look at my achievements through the home button, without having looked through the dashboard, does nothing and it works fine. but as soon as i look through the dashboard the error happens again.
does anyone know why it is this is happening, i'm afraid that it might end up completely wiping my gamer score for good. any help will be much appreciated, thanks.