Headset major problem

Ok i have a turtlebeach x11 really there for xbox but i use them on the pc they have been fine for ages but just agter i installed my new gfx card (ati xfx hd 6870) they have been acting up. when i play game ie cod4 there fine until i get into the game there fine in the starting menu so on its just when im actualy playing my freinds are saying it sounds like theres a wasp or something flying in my mic,today i signed on ts3 and there all saying im echoing there voices back so i left just to be nice but these problems cant carry on there doing my box in...
any idea of the problemmrolleyes