http://support.wdc.com/download/index.asp?swid=1

If your drive is not listed contact them directly for an alternative tool. If it's on warranty return it and get an internal drive instead. External drives have many, many problems

If this doesn't show a problem I'd suspect the motherboard. Did you try a different USB port?

Track down your mother board and make sure there isn't a new drivers for it, for external drives.