Awful NS performance(poor FPS)

Opprobrious

My current system
OS: Windows XP SP3
MB: A8N-SLI Premium
CPU: AMD X2 4400
RAM: OCZ Platinum 2GB SDRAM DDR 400 2-3-2-5
Video Card: Radeon HD 4850

I'm having serious fps problems while playing natural selection.

Simply viewing PGs or flashlights causes significant fps drops.

I stress tested my CPU and it never gets above 48C after almost 30 minutes under full load.

I'm at my wits end trying to figure this out, it is extremely frustrating to not be able to run this game with acceptable performance.

Faskalia

Set affinity for NS to a single core and set its priority to high.