This has happened to me in the past. It's intermittent, so it's hard to track the issue, but may I offer a few options for troubleshooting the problem.
This solutions uses Terminal. Go to your spotlight and type "Terminal" and open the application.
List the current drives:
- Plug in your USB drive. Wait at least 30 seconds.
- type
diskutil list
- Go through the list of drives and determine if your drive is showing up
It should show up, since it is showing up for you in DiskUtility. This tells me that it isn't mounting properly. Try mounting it now:
- If unable to mount as a regular user, do a
sudo
when executing the command: diskutil mount /dev/disk#s#
, where disk# is your i/o port and s# is the actual drive. So be sure you get those numbers right by following the steps above.
- If it mounts properly, go ahead and try to repair it with DiskUtility. If it doesn't then sometimes by restarting the computer and going into the recovery partition may be able to give you better results, since it's loading OSX to the RAM instead. Be careful not to mess with other disks/partitions.
You can also try to repair it manually in Terminal. To do this, open a terminal window and do the following:
- List volumes:
cd /Volumes
- Once you know the volume name (drive ID), type
diskutil verifyVolume [your volume name]
- If it doesn't give you any errors, then repair it:
diskutil repairvolume /Volumes/[your volume name]
If after doing all this, you still have issues with your drive, I would try using a different Mac OS X computer (not Windows)
cheers