A couple of friends and I have also been having some trouble, I've went from level 7 to 3, my only suggestion is to wait it out, till it gets fixed, then again, every game has a couple of glitches in the first day or two.
But, I'm sure it will be resolved very soon.

had the same problem myself.

some causes ( i think )
Dashboarding while playing online
Leaving a online game before its over
or just a bug in the game

or a huge conspiracy to make you mad as hell just like the extreme track

I had this happen to me the yesterday. I was a level 6 and reset back to 1 because my xbox froze. It could just be a glitch that does cause it.

Wow, so it wasn't just me, I'm glad I know the problem now. thank god, err... thank this post.

Yes, it's a regular occurrence for my friends and I.

I have gotten very frustrated with it, so I'm just going to erase the game and DL it again later.

You're not alone Sean.

This is because of the quit system they have if you dashboard or turn your xbox 360 console off during the game you'll be deranked to prevent this you got to save the game(autosave) and then go to where it says "Press Start" and then go to the dashboard then turn your console off or go on another game

Thanks

-Laser-

This is very frustrating. Happened to me a few times.

Normally my xbox freezes on the game and once I come back on I'm down a few levels. Went from 26-24 when my game froze after a race.

Lol,, Nice find though

Could be anoying thou

I to had this problem and i am level 18 i just rang up the support server and in less than an hour they reset my rank back.
I also gathered information that they are aware of many issues to do with multiplayer and are putting updates into play by the end of next week hopefully.