The best way would be to go through all the code and find where the sound command is. A messy alternative would be to rename the sound file which is causing you the problem.
I have no idea, why don't you try it and let us know.
I would go through all of the objects 1 by one and comment out all of the sound commands. Once no sound is playing, reintroduce them one at a time where you want the sound to play.
UPDATE : Renaming doesn't work, and neither does taking away the linkage name. The error is most likely because of a manually placed sound. Will try and see what happens when you take away the sound...