External hard drive used to work but no longr

Hello,

I have a 1000GB external hard drive (Seagate 1000GB SATA-2 7200 RPm) attached to an IMicro SATA 3.5" to USB Enclosure. The device has been working for about 8 months, but now when I connect it to my computer it no longer recognizes it. I tried connecting it to my laptop as well, and it doesn't work there either (although I had never connected it to my laptop). I can see a green LED light on the enclosure, and it uses an external power source. I have disconnected all other USB devices as well.

What could be the problem? Is it possible that the enclosure doesn't work, but the hard drive is fine? If the hard drive failed somehow, wouldn't the computer still recognize a USB device of some sorts? Or maybe the USB cable has somehow gone bad?

Thanks for your advice,
-Matt