iMovie 09 playback(full-screen) choppy during titles and transitions.

When I insert someting like a moving title, or a fading transition into my movie: the full-screen playback (and not the playback on the viewer) gets choppy or skips a movement. It specifically happens where the screen should be fading/transitioning or when a title should be moving/fading onto the screen. I have all the updates for 09 and I'm pretty sure that if this is the case on a full-scree, it would defenitely happen on a published exported version.