I don't think the loop buffer works. It is set at 30 seconds, but nothing is ever added to the recorded videos and there seems to be no way to 'enable' it.... :SHave you tried using the loop buffer in fraps to solve your issue? So you're sort of recording, but not really until you press record for proper and it adds on the loop buffer at the start. If you use loop buffer but don't start proper recording it may still be running the stuff that fixes your stutter.
Weird "fix" by the way - using an app that you'd think would add an overhead.