Corrupt files when transfering Audition projects to another user

Hey friends, I seem to have a problem when I transfer a project to a colleague. I work on a timeline in Audition and after I export a session and send it over, the other person gets this prompt when opening the project. All of the files are in the Imported folder, everything seems to be in place, but still this message appears: "Error: Corrupt File: not a valid RIFF file." Is the RIFF header something specific on Windows or is it Mac compatible as well?

Can somebody help please?