(Update: I read http://uk.gamespot.com/pages/forums/show_msgs.php?topic_id=25958198 and it explained why I lost them :()
I hook up my xbox360 to xbox live for the first time in five months, and it asks me to sign up for an xbox live account, so I enter my old one, and it says "do you want to retrieve your gamertag" or something, and naturally I say yes.
Now I see most of my achievements have disappeared as well as my gamer points??
No Civ:Rev score (in fact, not even a record of it), no Bioshock achievements, no Lego: Indiana Jones, what's happened???
Update: I downloaded an old profile that was stored online and overwrote my existing profile. Strange thing is, I never changed xbox 360 consoles!!??