I've NEVER seen that ever. You might be in a hacked lobby. Not sure.

For a start, this topic has been answered many times in this section of the forums, you didnt search well. open steam, go to library, right click on MW3 multiplayer, click properties, verify intergrity of game cache. this will check you local files and download fresh ones if it realises something is different from what it should be. if this hasnt worked for you, you will then need to navigate into you steam folder, usually C:/prgram Files/steam/ steam apps/ user data (or players, cant remember exaclty) and manually delete them. then when you verify, fresh clean files will be downloaded. i believe its a config. file you will need to delete.

All you need to do is delete your mp_cnfg.cfg:(you'll find it in X:/program file/steam/steamaps/common/MW3/player2)

the game will rebiuld a fresh one the next tyime you start the game; then just reset all your options. Hope this helps