Mount a Time Machine backup disk that will not mount I just plugged in my external hd via USB for a Time Machine backup. However it will not mount. 



I've:


Unplugged the hd
Restarted the computer
Plugged it back in


When I do this, Disk Utility spins and won't load. So I then:


Unplug the disk
Open Disk Utility
Plug in the disk and that shows the image above


When I press mount, it says the disk is already unlocked. However it will not show up.

This started after I tried repairing the volume, but it wouldn't repair. Now I can't select it. 

Any options at this point other than erasing the whole HD and starting over?
I've had problems like this also. If you have multiple USB ports try using a different port. Also try using a different cable and a different port.

You don't want to use a flaky drive for your backup. So, yes it seems like reformatting the drive and starting over makes sense, or replace it.