I had problems that my Maxtor USB disk wouldn’ mount on USB port on my WD My Book World Edition I. I update firmware to newest version but had no success.
So I connected a 4 port hub, to WD USB port, and connected USB cable to this hub.
This way everything worked fine and I was able to format the USB drive (even if WDC doesn’t recommend this). However after some some time the drive became disconnected again, so this might be only a temporary solution.