Won't save Audio file project

There is probably an easy answer to this, but I am getting a message that says "STP can't save the audio file with the [name I am using]". I have tried renaming many different ways (no spaces/dashes/dots, etc.) and that never helps. Sometimes, on different audio file projects, I haven't had this problem. Does it have anything to do with the preference it asks you in the box about "saving as a reference file"?