This one has me baffled. I have an external 1.5 gig USB 3 hard drive that's worked fine with my 6 month old macbook pro up until a few days ago. When I plug it in, it doesn't mount. As a matter of fact, it doesn't appear at all ... not in the disk utility or even in the "system report" under the USB in About This Mac info or in a new finder window. The drive lights up and I can hear it working but it's non existent. Now here's the odd thing. I can plug it in to my Mac Pro and it mounts fine and works perfectly. I'm using the same cable so that can't be the problem. And yes, I've tried both USB ports on my macbook pro and restarted the computer as well. Would anyone have any possible explanation as to why a drive would just stop mounting and showing up on one computer but work just fine on another?