Imovie 11 wont work after replacing files

[Tractor Torque]

Hi folks. Im using I movie 11 to edit a 2hr DVD. All was going fine until i realised i had imported one of 4 events at 720p setting. Rather than start again from scratch I imported the event again at 1080p and wanted to replace the project files like for like but as soon as i replaced the first file the viewer screen stopped working. I can still hear the audio but no picture. If anyone sould help I'd greatly appreciate it.

 

[Dave Braine]

I know you'd rather not, but try starting a new Project from scratch.