This usually happens either when you launch a previously saved your muvee project file where:

1. You have imported your media/source files from an external source/device such as a thumb drives, CDs, portable hard disks or network drives etc.

2. You have moved your media/source files or renamed the folder they are located at.

When you relaunch such a project, muvee autoProducer attempts to locate your media files from the location where they were last imported. Make sure your external source/device is connected so that your media files can be accessed. We recommend that you copy your media onto your computer's hard drive to avoid situations like these.