“Firefox is already running” error message when starting it
Firefox has not been closed properly and the profile lockfile has not been deleted on exit. This lockfile is used to prevent the profile to be use twice at the same time.
Solution : Remove the profile lock file
Operating system | Profile folder location(s) |
---|---|
Windows NT (NT4.x/2000/XP/Vista/7) | “%APPDATA%\Mozilla\” |
Windows 95 (without Desktop Update) | C:\Windows\Mozilla |
Windows 95 (with Desktop Update)/98/Me | C:\Windows\Application Data\Mozilla\
C:\Windows\Profiles\<Windows login/user name>\Application Data\Mozilla\ |
Unix/Linux | ~/.mozilla/ |
Mac OS X | ~/Library/Mozilla/
~/Library/Application Support/ |
To fix this, open the profile folder and delete the file,
“parent.lock” (Windows),
“lock” and “.parentlock” (Linux), or
“.parentlock” (Mac OS X)
For Mac OS X: You need to use a free utility like Onyx or Maintain to turn on visibility for invisible files to show “.parentlock”. This file contains no information, and deleting it will unlock the profile.
For Windows: If you attempt 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 (e.g., Chkdsk in Windows 2000/XP/Vista/7 or ScanDisk in Windows 98/ME).
Source : http://kb.mozillazine.org/Profile_in_use#Remove_the_profile_lock_file