Ok. I don't think the above console message has anything to do with my problem. It was a one off, so to speak. It has not appeared since.
I found that looking at the permissions for the iLife apps, iMovie differs. Where the other apps list "system" as the owner, iMovie lists myself. Using chown in the terminal, I have rectified this with the following command:
sudo chown -R system:admin iMovie.app
Excited, I rebooted and launched iMovie. NO change. Only the title "organic main" displays incorrectly, everything else is fine.
I'm probably at the end of my knowledge and abilities. Are there any any suggestions?