Gorden has given the obvious answer, and most likely to be correct.
However...
It could also be a duff usb port and quite like a duff usb /lead/ producing these errors. The latter is surprisingly common with usb 2.0 (and for all I know, 3.0 too).
Try different lead and port - although the corruption could exist on the fs caused by problem writes caused by a duff lead.
(read on further). You got it mounted, great! But if you continue to have issues, before you fling it, try a different lead.
