Thanks for the details. We have a similar problem (see my post below) and are in the process of adding back each clip and then testing for export. My question is, once iMovie is unable to export the project, does it render the file "bad" and prevent exporting even if you remove the "poisned" clip(s)?
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Hello, We are having a similar problem running iMovie '09. We get the exact same error as you reported.
"Unable to prepare project for publishing" The project could not be prepared for publishing because an error occurred (-50)
We have a very similar situation were we have multiple repeated clips. However, our clips are 2.4 's. Like you, we took the finished project and started eliminating edits that we thought might be preventing it from exporting. The following actions still would not allow the project to export:
When we create the new project from the recorded event without making any edits (just as recorded), it exports without issue. We have started the arduous task of adding back in each edit and testing it for export until we determine which edit is causing it to "not export". This is a very inefficient way of troubleshooting.
This is a science project for my son and we need to be able to save it as a QT or mpeg4 movie so that he can submit it to his teacher for viewing and a grade!
Any ideas from any other users would be greatly appreciated.