Over the past few days, some players (including myself) have noticed that their stats from games of Halo 3 have not been uploading to Bungie.net. The issue involved corrupted data that, in the simplest of terms, wasn't connecting players to their game data. The data still existed, the games just had to be relinked to the profiles.
Because of the way our database works, the most recently uploaded games affect the Player Bar at the top of your page. So, while the reprocessing is underway (it should conclude in the next 24-36 hours), things like your Rank and EXP may appear differently than they appear in game, specifically, they may appear how they were on say, last Friday. The good news is that the in-game display is correct and will be reflected on the website either after you play another game and it uploads, or one all of the processing is complete and you play another game -- that's because of the "most recently updated game history" bit I was talking about above.
So if your displayed rank, EXP or anything weird is showing up on your stats page, we're aware of it and it's the result of maintenance we are doing to keep everything current. Don't freak out, top men are on it.