Aperture: Metadata import/export issues (IPTC, keywords, EXIF)This sounds like a problem I've had with PictureSync. I know GraphicConverter also rewrites EXIF headers, I wonder if it's vulnerable to this problem.
Issue: Aperture won't import certain files with added metadata
Under certain circumstances with certain cameras, Aperture may not be able to import files which have had metadata added by Photo Mechanic or similar applications. Sometimes the file may import but then result in an 'unsupported format' message.