Did you try setting your FPS recording on fraps to 60 frames per second to match your game? That usually works, but if that doesn't then you might want to check the write speed on your hard drive just to be safe, and if all thus fails try settings your Full quality setting, to Half-size. Generally fraps is a lagfest of a recording program on multiple grounds. I have problems with it myself, but you should try another recording program such as Dxtory if nothing works.
Quick Edit: Rarely, but usually when you have your computer on for a long duration of time without shutting off, then your ram may be stored up to its neck with memory, so fraps has less resources to work with. Restarting your computer usually diminishes some lag.