Hi guys. I had some issues today and thought I'd share them in case anyone else is suffering. :)
I run Sonar Platinum and Focusrite interfaces.
I was just about ready to smash my PC today. After 3 hours of struggle, while trying to mix tracks for work and dealing with horrible glitchiness on a machine that should never have such issues, and removing every plugin I could from my session in an elimination process (except 1...), I finally figured it out.
I had the Drawmer S73 on the mix buss. It was bypassed. I turned it back on and the machine stopped glitching. Bypassed it and the track stuttered like crazy. Removed it completely and it's fine. I emailed Softube about this today to let them know.
Good luck!