Another poster says this works for this problem.
I tried everything above and in other posts and nothing worked.
All I did was opened the problem project and hit select all and copied all the clips.
Then I went back and started a new project so I wasnt messing with my good copy. Paste your clips. (you will only have your video clips and not any audio.)
At this point just start from one end or the other and delete one clip at a time and try to export.
You should keep getting the error until suddenly it works.
At that point you know the clip you just deleted was the problem clip.
Go back to you original project, find the problem clip, give it the boot and replace it with a nice fresh one.
Export or share and take a deep breath."