I know this has been answered in another thread, so this is for anyone else stumbling across this one with a similar question.
AMD cards are not optimised for Folding at Home like nVidia cards are. As such, expect low scores from them.
On top of this, folding on your AMD card may very well not be worth it. Graphics cards take some power away from the CPU when they fold, lowering the SMP PPD. With a situation like yours, folding on your GPU may actually be causing you to get less points altogether.
Edit: 'dis is why I need to type faster.