USB 2.0 hard disk does not show up I have a 15-inch Macbook Pro with Retina Display that doesn't work with my USB 2 hard disk. It doesn't mount, doesn't show up in Disk Utility, and doesn't even show up in System Information  in the USB section.

This hard disk works fine on my Ubuntu desktop, and it worked fine on my previous Macbook Pro (2009 model). It doesn't work on my new Macbook Pro, but another disk does.

This is a bus-powered drive. I tried rebooting my Mac, and plugging into a different USB port. The LED comes on when I plug it in, but that's it. If I put my ear to the disk, I hear mild clicking sounds (but I am not worried about data loss since the disk works great on my other machines, every time, without the clicking sound).

Any idea what I can try? Use an AC power adapter? Thanks.
Try using a USB - Y Cable! As the others have said... It appears the drive is not getting enough power. 

Example,
http://eshop.macsales.com/item/OWC/USB3AYMBPB/

I realize that is microusb but they make y cables with USB on all the ends.

Goodluck! :)