This error message may appear when you try to burn your project to a disc. Start by trying to export all the movies in the project as files and then opening a new, empty project.

To do this, follow these steps:

1. Go to "File" > "Manage Movie" > "Export" and save the MVD file in a folder that's easy to find. If your project contains multiple movies, you can use the movie tabs above the timeline to switch between them. Export each movie separately.
   
2. Create a new project.
3. In the Media Pool, open the folder you exported your MVD movie files to. Import the movies into the project one after another. Be sure to import them in the right order. When the program asks you what you want to do if a movie is already open, click "Do not close".
4. Burn your project to disc.