Update your drivers, check which Codec Fraps is using, check teh FPS fraps is set to, update the codec fraps is using, update fraps, get a new codec, use a better program
I use Dxtory because i hate how fraps makes things laggggggggg, i have a high powered PC, but im used to high FPS, any major loss in FPS makes gaming hard for me, Dxtory doesnt seem to affect the FPS at all, plus is overall a better and more advanced program.