Your CPU might be a bottleneck.
1. Make sure you install the new drivers AFTER uninstalling old drivers from previous cards.
2. Might be your PSU.
3. Defective card (Highly unlikely but possible).
I recently upgraded my graphics card and my FPS went from 25 to 60 - 80 (around) in Combat Arms.
EDIT: I just played CA right now (OMA 4 people in game). My FPS is 100 - 135 and lobby FPS is 250 - 270.