
click to enlarge
This one doesn't work so well if you had a Mac Mini copy failure to your USB flash drive because the flash drive won't even show up on your desktop, but if the issue is elsewhere, it's a great idea to reformat the device. To do this, insert the flash drive firmly into the port, open up "Disk Utility" and highlight your flash drive. If you look in the upper middle, you'll see an "Erase" tab. Click this, change the formatting option to "MS-DOS (FAT)", and then select "Erase". It should take just a few seconds (maybe up to a minute) to do this, and then you should be clear to go.
Note: Formatting your USB flash drive will destroy all data on the drive.