I use the NitroAV card every night to back up my MBP. As was mentioned above, you have to pay attention to the power state via the little card icon in the menu bar. I have had little trouble inserting the card, turning on my external drive, and having the MBP mount the drive. When I'm done with backing up, I unmount the drive (from the finder), click on the menu icon & select "power down card", and turn off the drive, then remove the card. On rare occasions, when I plug the card in, the MBP fails to see it. As long as I do things in this order, I've had almost no trouble.