Audition won't recogize a wav file recorded on a different computer

I am currently working on starting a podcast with a friend who lives in a different state. We were practicing talking via Skype while simultaneously recording on our respective computers. My plan was to take my friend's audio file and synch it with mine to be sure it sounds right. However, Audition always gives me the same error message no matter what I've tried doing:

I record on an Asus using Audition. He records on a Mac using GarageBand. I figured having him send me a wav file would work just fine since it's a universally recognized file type, but I can't get this to work. I probably have a beginner understanding of all this, so any help is appreciated. Please feel free to ask for additional information.

Thanks you.