First, the specifics of what drives are affected and what the symptoms are. For me it was external drives, irrespective of connection type. This means it’s not limited to just USB, or just firewire but is equally applicable to eSata and network volumes.

The problem is very subtle, the first symptoms for me were scheduled backups that failed with error messages telling me that destination drive is unavailable. This was despite me being able to see the drive in the Finder window.

The exact symptoms will depend on what you use the external drive for but for me problems included:

– Lightroom unable to locate the catalog
– Aperture unable to locate database
– iPhoto unable to find library
– iTunes unable to find database file and/or media files
– ChronoSync failing to locate backup drive
– Email Backup Pro failing to backup
– MailSteward failing to backup

From my research TimeMachine would also fail to function correctly as well.

The problem stems from OS X deeming that the drive in question has been ejected illegally. This can happen when a Mac sleeps, crashes or kernel panics. When the Mac is rebooted the drive is mounted but instead of mounting using the drive name it is mounted using the drive name and a number tagged on the end. So for me "Current" became "Current 1".

Confusingly this is NOT displayed in the Finder which still happily refers to the drive by the expected name in my case "Current".

The easiest way is to ascertain the mount point name is to use Disk Utility.

Select the drive name from the drive list on the left of the window (1) and the mount point name is displayed in the information below (2).

The easiest way to fix it I found was to use PathFinder.

You will need to be able to access hidden files so select View > Show Invisible Files from the PathFinder menu.

The next step is to navigate to the root of the Macintosh HD and locate the Volumes folder.

Inside the Volumes folder you should find shortcuts to all the drives on your system and at least one folder with the same name as the drive with which you are having problems.

Here I have a folder named Current (1) and a drive called Current (2).

Move the folder to another location.

You may need to authenticate in order to be able to do this so enter your password in the dialog that appears.

Select View > Show Invisible Files from the PathFinder menu to hide the invisible files.

The final step is to either eject the drive with the "+1" mount point or reboot. Either of these options will ensure that the mount point is reset to the original name and all the applications and processes should run as previously.

There are of course several other ways to remove the offending folder so PathFinder isn’t a requirement but for me it’s the fastest way to do it and I’ve had to repeat the process more times than I’d like so I’ve got it down to a fine art now.

The other methods involve using a system utility, such as Onyx, TinkerTool or Cocktail to show the invisible files and Finder to locate and remove the folder. Alternatively there are Terminal commands available to achieve the same result.

I hope you never have cause to use any of the fixes but if you do I trust these steps help you.