Imovie File Corrupted


i have been using imovie 4.0.1 under OS X 10.3.9. I can't open my .iMovieProj file. I get the message 'your project file is not readable'. The .mov file is fine and can be read in quick time, but I need to do further editing, and would like to reopen the .iMovieProj file. Is there any way to deal with this? Thanks, Dennis