The most immediate answer I could offer would be to Re-Install minecraft perhaps if you don't have too many addons that would be a pain to re-install. Otherwise, perhaps check to see if you have the most up-to date versions of Java?
Yeah, FRAPS can be a CPU hog, I've never had too many issues with it, if you're okay with sacrificing a little quality at higher playback resolutions, you can always capture half frames instead of full. On an older comp I had it was the only way to get halfway decent framerates. But your comp shouldn't be struggling that much if its new... :/