error -50 when trying to share with media browser?

I'm attempting to burn a dvd in idvd for the first time. When I click media browser under share in imovie 08, I'm fist told that there's missing media. A source clip is not available. Although I hear it (audio) in both the project and in the source material in the event library. I clicked continue and things started to move along then this warning came up UNABLE TO PREPARE PROJECT FOR PUBLISHING ERROR CODE-50.

Please help.