Random stutter when turning with mouse..

[Stabulous]

I hold right click with my mouse to turn and some of the time when I try to make a turn my game will just randomly hitch a little and turn me too far. It's pretty disorienting when it happens, a lot of the time if there aren't any landmarks around I have no idea what way i'm facing after it happens. I turned my win 7 aero theme off because I read that p99 doesn't like that. I also put my max fps in my game options to 60. Is there anything else I can do to alleviate it? It only happens when i'm turning with my mouse, which seems weird to me. I set my /mousespeed to 4 if that matters. That's what seems comfortable to me. Thanks.