Earlier today, many Xbox Live users began to report that their Gamerscores had been reset to zero and their achievements had been cleared out. Thankfully, word from on high (as well as on the 'net) is that everything's now been fixed, so there's no longer any reason to worry about booting up your 360 for fear that your lifetime of gaming accomplishments would be wiped clean.
Here's the official mea culpa straight from Microsoft:
The issue that some customers were experiencing with zero Achievements and Gamerscores has now been resolved. We apologize for any inconvenience this may have caused.
If you were unlucky enough to be affected by the bug, you may need to log in and out of your Xbox Live account to get back all those hard earned points. If that doesn't work, you'll need to redownload your profile. Instructions for that can be found here on the official support site.
