My MW2 Challenges have been reset and LOCKED?

I was playing a *NORMAL* game on Call of Duty : Modern Warfare2 and it turned into a hack room and started to de-rank me. I left the game as soon as i could by my challenges were reset and some of my titles and emblems lost. I then played a normal game to try and complete some of the challenges but when i finished the game my challenges were still the same and i didnt unlock anything (i got more than 10 kills with my ACR but i didnt get grenade launcher for it) How do i fix this??? I'm seriusly considering of making a new PlayStation Network account and restarting the whole game. THANKS FOR YOUR HELP