We are aware of some compatibility issues with the SanDisk 64GB Mobile Ultra microSDXC memory card.
The issue plagued us and SanDisk’s customer base last year but died down. It would appear that the problem has come up again.
We are in the process of conducting a full investigation on the matter and will be better informed after this weekend.
In the mean time, the Kingston and Samsung 64GB microSDXC have had no reported compatibility issues.