Where is this audio file coming from?
Many music files, especially music and audio downloaded from iTunes, includes copy protection software that will prevent you from using it in a video project.
Premiere Elements has problems with iTunes and other music whether or not the music comes protected.
Typically the answer is to convert the music to WAV version in iTunes using the following iTunes how to.
I have been through this process for unprotected music so if any questions or need clarification on this type of solution, please let me know.