Question about iMovie '11-->'09 Compatibility

[jsin]

Hi there. I recently started making a movie in iMovie 09 on one machine, moved the project file to another machine for a bit that had iMovie '11, and now need to move it back to the first machine. I've moved the same files back that I started with, replacing old ones with the ones I updated (iMovie Events and Projects folders), but now my project (top-left pane of iMovie) does not show anything. I made sure my project file is in the correct place (I know it is, as my other old projects show up), and I also searched for duplicates just in case. Ultimately, I suspect that I cannot move an iMovie 09 file to '11 and back to '09 again. Is that so? Any advice is appreciated.