the card might be incompatible. You should try the following:
-Macs do format HDs as FAT (MS-DOS). Under Disk Utility in OS X choose Initialize, then select the format. You will have 4 Mac OS choices plus (at the bottom of the selection window) MS-DOS (FAT).
After that, try to store presets to the card. That tells you if the card is compatible or not.
Other than this, I may think of bootloader needing update…but let's try these suggestions first.
Please let me know.