Your version of [cocoaDsk] must be updated. Please download the current version http://sidhome.free.fr/Projets/CocoaDsk/Release/CocoaDsk.app-1.08.zip.
What's new : Manage your Amstrad CPC computer range floppy image disk directly with OSX. Just jump to the link to know more.
Thank you for using my softwares ;). Jerome.