Error: File not supported by any currently registered plug-ins.
Note that some of the features from Audition 3 (like CD burning and tone/noise generation) are missing in Audition CS 5.5 but will be back in CS 6 next year.
Edit: 2 questions to klonuo: 1. Did you have to download the entire production bundle to get this Windows version? It seems Audition CS 5.5 cannot be downloaded separately (yet). 2. Did you have to do something special to get "libsndfile" into the "Supported formats" list, or does it come like this out of the box?
...Output formats are limited to WAV/AIFF/MOV(audio) and additional MP3 (FhG)