The good news is there is finally a hard drive copying mechanism that requires no computer!
You will need to remove the hard drive from its external case and put it in that mechanism, but at least it will solve your file copying issues.
http://the-gadgeteer.com/2010/03/30/startech-satdock22r-usb-to-sata-standalone-h ard-drive-dock-duplicator-review/
I don't work for Startech, just am a very happy customer.
That's just something to keep in back of your mind should you end up getting a new drive.
Since the drive is USB, it likely is getting hung by other USB devices on your system. Go to Apple menu -> About This Mac -> More Info, and select USB.
Make sure the hard drive is not on the same bus as other devices. Every single item on the same bus can slow down the hard drive.