If your Seagate GoFlex hard drive doesn't connect to your computer. This may be the reason why. A loose USB connection may allow the drive to spin up, but not allow data transfer.

UPDATE: ordered a cheap SATA to USB adapter cable from eBay. It works with minimal modification. I had to take the enclosure apart and enlarge the opening to accommodate the larger end, but about 10 minutes with small flat screwdrivers and an utility knife and it was good to go.