This error can occur for many reasons.
1. If you are about to save a soundtrack and you rename the default file name you will need to append a ".wav" extension to the end of the new name.
2. If you add a new audio palette, then you add a destination path pointing to the CDROM drive everytime the application starts it will look at the CDROM drive for the sound files it needs, and if it can't find them it will give you an error message. You can fix this by simply removing the destination path that is pointing to your CDROM drive.
Likely Reason: A clip failed to export as a movie. (issues may include: not enough disk space available, low memory conditions, file name already used and existing file was not deleted)