Thunderbird Cannot Use The Profile Because It Is In Use

If you are getting an error message from Thunderbird that looks something like this

And, restarting your computer has not helped, then, this solution may help you.

Remove the lock file in the profile folder

The Thunderbird software may may have shut down (terminated) incorrectly (abnormally/crashed), and thus leaving the lock file in place. To fix this, do the following.

1. Locate your profiles folder.
   On a windows system, it is most likely located somewhere like this: C:\Documents and Settings\Owner\Application Data\Thunderbird\Profiles
   For example: C:\Documents and Settings\Owner\Application Data\Thunderbird\Profiles\rvq9il7z
   
   
2. Delete the Lock File.
   
   
   1. On a Windows computer, remove (delete) "parent.lock"
      
      
   2. On a Linux based computer, remove (delete) "lock" and ".parentlock"
      
      
   3. On a Max OS X computer, remove (delete) ".parentlock"

NOTES:

Windows: If you find that you are not able to delete the "parent.lock" file and receive the error, "Cannot delete parent: The file or directory is corrupted and unreadable", restart the computer and run the system error-checking tool (such as Chkdsk in Windows 2000/XP/Vista/7 or ScanDisk on Windows 98/ME).

Mac OS X: You will need to make use of a free utility like Onyx, or Maintain to make visible (show) the file of ".parentlock". This is an empty file, and just signals that the profile is in use, even if it is not.  Deleting it will unlock the profile.

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