I just logged in and I'm currently playing Bad Company 2 and for whatever reason my stats were reset for the Vietnam DLC.  If you're wondering I don't pad my stats I literally haven't played the game in about a month.

the stats are really broken in-game, if you want to still track them i suggest using a website like statsverse thats what i do.

I think everyones stats are broken.

Hell a couple of times i've started a game and the damn thing thinks i'm level 1 and doesn't let me use my unlocks! It also keeps telling me that i'm either skill level 200 or 0, it is just messed up.
 
 
I do sometimes look at this one though 
http://bfbc2.statsverse.com/

interesting, interesting, before I check out statsverse it'll begin tracking my stats from the point of registering or will it look through all my time playing?

Everyone's stats are broken right now at least on the 360. Chances are if you join a multiplayer game you will start as a rank 0 scrub without any of your unlocks. It's some problem they've been having these past two days now.
 
It seems that if you play a couple rounds or so you regain your rank and all your stuff but if you leave the game you will probably lose them again.

My brother was having this problem too. How strange.

This isn't the first time. In fact, when they did the TNT with BFBC2 a few months ago the stats were all busted at the time and everyone was either defaulted to the AEK, 9A-91, PKM, and M24 -- or if they had the spec-op weapons, they could use those. There is no way they would ever lose everyone's stats. They probably have triple-redundancy on data servers across the world.