Then I would advice to remove any remark in the marketing materials as they do contain remarks about OSX. I'm new to iRidium, but I really though OSX was a supported client based on the documentation.

Example: http://www.iridiummobile.net/upload/marketing_materials/Brochure%20about%20iRidium%20for%20End-Users.pdf

Also, speed can be an issue. I've noticed quite some difference in RasPi projects using different cards. So far I use 32/63Gb Sandisk Class 10 cards. They work ok and are pretty fast.