HI gang was woudering if any of you lot in your infinate wisdom could help me out

.I have recently bought an Nvidia 6600le graphics cardand went to play sh3,when the game goes to the sub pen at the start of a mission the crews faces and conning tower are grayed out??????and the games running very slow like when you are in external view and you turn from the open sea to the harbour it starts to lock up and jump.I had no probs with my Nvidia 5500fx graphics card.Could anyone giver me some advice on how to sort it out.Cheers in advance