I tried this on my Oregon 550 and it all works well ! First I selected the maps in MapSource and transferred them to a USBstick. Secondly I copied the created map (Garmin) to my harddrive and used Fast IMG Unlocker. Finally I copied the Garmin map to my Oregon. At startup I got the message "Can't authenticate" but after clicking on OK, all the maps I selected/copied were (de)selectable and useable. This workaround works well with the new securitymethode with gma-certificates.