I have a 1.5T seagate freeagent goflex USB external hard drive, use to work well on my 2011 13" MBA. It stop working today, no sign after plug in the USB cable, the light on the drive is on, but no drive showed in Finder or on the desktop. The hard drive is good, as it can read/write on a windows PC and on a 2010 MBP. The USB ports on the MBA are working, as it can access iPhone and a USB flash drive. I try another USB external hard drive, no go. I cannot remember if I ejected the hard drive when I unplug it last time. Any idea how to fix the problem.