Possible Driver Problem?

This is a weird issue that I've been having for some time now. I've had my HD3850 AGP card for about 2 months and its been nothing but what i thought it would be except for CoD4. If i have the AGP Read option in Catalyst enable the game will basically play frame by frame until i look down itll run fine but thats all i can do is look down. With AGP Read set to off the game runs fine but not as fast as it should be. Also when I have catalyst up on my 2nd screen with AGP read on it wont use any of the GPU until i look down then it will use 99%(Max) of the GPU. But with AGP Read off it only uses 30-50% hence the poor frames. I've tried all patches and new installs of CoD4 also many different drivers. Even tried reformats to no avail. I'm using XP Pro SP3 and CoD4 is the only game that does this.