Call of Duty: World at War

Hi,

I purchased Call of Duty - World at War rcently and sometimes when I play on multiplyer it says "this key is being used by another computer".

Is there a way to resolve this?

Is there a way to bind a a key to me to make sure it can't be stolen?

Can I be issued a new key if this is the case?

This is very unfair as I purchased the game and this ruining my online experience.

Regards,

Gilittle