Apple Aperture 2 is very flexible regarding importing files. However, I have discovered that if you have symbolic links in the path to your image files, Aperture 2 will report the file as an unsupported format.
Case in point: I added a data drive to my Mac Pro and moved all of the data over to it. However, OS X expects the “Documents”, “Pictures”, “Music”, “Movies”, etc folders to be on the system drive (the one where OS X is installed). I created symbolic links (shadow copies in Windows terms) to the folders on the new drive pointing to the location on the old drive.
Under normal circumstances, this arrangement works well. The OS handles the translation seamlessly and everything is hunky dory.
Except Aperture 2.
Aperture 2 imports the files just fine, but when it comes time to render the previews – “Unsupported Format”.
The solution: import the files using the real path (no symbolic links) or import the images into the Aperture Library directly.