iMovie Export Issue

There could be a fault with iMovie.

If  iMovie starts behaving unexpectedly in any way for no apparent reason, the problem could be caused by corrupt preference files. 

The cure for this is to delete the preferences. 

 Hold down the  Cmd and Option keys as you launch  iMovie and this window will appear.

Click “Delete Preferences” and  iMovie will open in the default (as-new) mode with sometimes no projects etc. on the interface. 

If your project doesn’t load automatically you will have to navigate to it and reopen it.  Your project libraries by default are stored in your Movies folder unless you have specified somewhere different.

It might be that you don't have enough space on your destination drive to import a 90 minute movie, that is pretty large. So the export aborts before being completed, leaving you with a temporary file on your desktop that you could not open or play, as you have observed. Or possibly there is some corruption in the movie that is causing the export to abort.

Check how much free space you have by going to Apple Logo/About this Mac/Storage. If you are saving to an external drive control-click on its icon, then click on Get Info and check the Get Info box to see how much available space that you have. Also, if your external drive is formatted FAT 32, there would be a 4GB file size limitation that is causing the export to abort, since your movie is a lot larger than 4GB.

As for the possibility of corruption in the project, you can expand your timeline and scroll through it looking for signs of corruption such as black frames, white flashes, artifacts, etc. Cut out any that you find and try again to export. Good idea to work with a duplicate so that you preserved your original work. You can narrow down your search by exporting, say, one half of the project and if it works then you know that the corruption is in the other half.

To rule out that the export problem is confined to just this one project, try creating a new project and then, in your original project do an Edit/Select All, Edit/Copy, of the media in it and Edit/Paste the media into the timeline of the newly created project. Your edits will carry over. Then see if you can successfully export the new project.

-- Rich