Why are my pictures stuttering?

I've been working on a slideshow project in Windows Live Movie Maker, and it always works just fine in Movie Maker itself. All of the pictures have an animation (zoom out center, pan up, etc.). When I save the project, two of these pictures always lag, no matter what. I've changed the animation and the picture, but it always lags at that same exact moment. It only lasts for the duration of these two pictures, and it happens like clockwork. Is there a reason for this? What am I doing wrong?