If you have QuickTime Pro and can get QT Player open (or another app that can recompress a QT movie) you can go to the iMovie file, command (or right-) click on it, select "Show Package Contents", and browse around within the package until you find the iDVD export .mov; that should be a version of the cut-together movie that you can then open in QT Player and export. I do this frequently to bypass iMovie for various reasons.