Hi
this might sound daft..but the cable you connect it with, try another one, in my experience ive seen these cables work with a printer but not a hard drive and work with some hard drives and not others, some say they are all cabled the same but i can tell ya that ive got various cables that all look the same but whilst one works with my tomtom satnav it wont work with a 2.5" hdd that i have.
even if its the original cable try another.
then come back and let us know, its a bad chance that the partition table is screwed up but im betting its the cable.