I don't use iMovie (FCP), but what are you trying to burn onto a DVD? What output medium are you trying to make. Is this for archival purposes? Is this a regular DVD?
If you want to burn a movie to DVD, what about iDVD? I haven't used iLife much yet (iDVD 3, iMovie 3, iPhoto 2, iTunes 3), but it's supposed to be easier than ever to use.