Try this workaround, it worked for me.
1. Open Toast & click on the audio tab.
2. Drag you audio files into Toast.
3. Once they have imported, select the music files you want and click on the export button.
4. In the save pop-up, select AAC format in the drop-down (AAC worked for me but you can try others if you want), also select a save destination for the files (maybe into your music folder it doesn't really matter).
5. Once the audio files have finished exporting you can drag your music files from wherever you saved them into Motion Pictures HD then click on Make Movie when You're ready.
It's a long winded process but the final result is worth it.