I have a 64GB micro SD card, inserted using an adapter into my SD card slot on my late 2010 MBA. The card was formatted as journaled, encrypted using disk utility. I want time machine to back this card up just as it does for my internal drive. When I go to Options in Time Machine preferences, the drive shows up as being excluded. I select it and hit the - button and it goes of the exclusion list. However, it doesn't back up and when I check Options again it has reappeared. Any suggestions? Thanks!