I have a new MBA that supports USB 3.0, and I just purchased a USB 3.0 external drive. The drive works great when I plug it into the USB port next to the MagSafe 2 port, but it's not recognized when I plug it into the USB port next to the Thunderbolt port. The power light does light up on the drive, but Finder can't see the drive. Any ideas on why this might be happening? Is there a difference between the two USB ports?