When I insert Lower Thirds using Ultimate S 2.0, the playback will stutter on the frames where Lower Thirds is applied. Why is it? This will not happen when I copy and paste the same Lower Thirds from it's original file.

Thanks for the advice.

If you're talking about choppy playback in the preview window, that has to do with processing power. Try lowering the preview setting down to 'good' or 'preview' if you have it set for best. That or get a more powerful machine.

The preview setting is "Good." And I am running a Dual Core computer with 1 GB RAM.

deleted by Vin

As far as I can tell, the differences between the lower thirds png file and the lower thirds placed by using Ultimate S2 are lower res (327x240 vs your project res), playback rate (1.0 vs 1.25) and the fade in/out. Not sure why your preview is stuttering. You might want to pop another gig of ram into that machine, just for general purposes. 1 gb doesn't leave much room these days. Not saying that will cure your stutter, but Vegas should run a bit smoother overall, especially if your running WinXP as your OS. If lowering your preview setting helps, it sure points to processing power as the cause of the stutter, at least IMO.