Aha, that might be it then! Two weeks ago I was doing single player offline and had 2 minutes to go to get one of the hard achievements. So I paused the game and connected to Live. No problem. Finished the campaign and got the achievement.
At that moment it wanted to save something but couldn't find the drive, so it suggested the default drive (duh...) and I said yes to overwrite it because I didn't think it would hurt. Turned out that I lost ALL progress up to that point. Although I had everything done on easy and medium it told me I had zero stats there. After that I went to the Achievement stat page of ET:QW and saw zeroes in every single case even the online stats!! Argghhhh!!! Turned of my xbox in disgust and did something else.
Later on I started the game expecting to have to start all over again. Checked my stats and they were back for the online part and the oflline showed the right stat for those campaigns I already had achievements for.
So I think something got crossed along the line. Seems to me that the game checks your Live achievements first and gets online stats from somewhere else (id, nerve, activision?) each time you check the achievements in the game.
Maybe the following is worth a try for you guys:
Start offline, play a bit, pause, connect to XBL, finish level, have it overwrite your save game, check stats, quit to dashboard (or power off machine like I did...), restart game, check stats....
But don't shoot me if this doesn't work for you :-)
cheers and good luck
>I've done questionable things.... Nothing the god of bio-mechanics wouldn't let you in heaven for.