How to increase recording FPS?

I've been noticing lately that my recording FPS is much lower than other peoples', even though my computer is about equal to, or better than theirs

How do you guys record at 40-50fps on a 512mb or less card?

My specs:

2gb ram
2.33ghz processor OCed to like 2.5 or so
ATI x1650 Pro Overclocked from 600mhz gpu to 680-690mhz and ram from 400mhz to 510mhz or so

I run CA on 1024x768 resolution and record at 60fps/half size. I have tried higher resolutions and a lot of different fraps settings but nothing really helps...

Currently record with: 60fps / half size / I don't record sound usually / force lossless RGB capture on. I will run anywhere from 50-150fps ingame, but as soon as I hit the record button it drops to 25-30 fps regardless of what map, scenery, graphics settings, etc...