"Thunderbird is already running" error every time I try to start Thunderbird, even if it is not running

Question

I cannot open Thunderbird. The process isn't running, but when I click on the icon, I get the the following error:

Thunderbird is already running, but is not responding. To open a new window, you must first close the existing Thunderbird process, or restart your system.

I've tried the following:

• Ending the task in Task Manager
• Deleting parent.lock
• Uninstalling Thunderbird
• Uninstalling Firefox
• Running Thunderbird in software "safe mode" and Windows safe mode

What can I do to fix this problem?

The problem looks more serious than expected. I do not see any Mail folder in my profile at C:\Users\your-username\AppData\Mozilla\Thunderbird. I think I lost my email.

Answer 1

You said you've tried ending the task in task manager, but have you tried ending the process in the task manager?

Does it ever work correctly, for example the first time after rebooting your computer?

Answer 2

As Meraj al Maksud noted, it could be due to file permissions. On mac OS, there’s an additional annoyance: access control lists (ACL). Recently, whenever I copy something (with cp -a) from an external backup, it gets copied with access restrictions that aren’t visible in the usual ls -l output. Among many other problems, this led to Thunderbird insisting that it was already open.

You can remove all ACLs using chmod -N, so chmod -N -R . will remove all ACLs from the current directory and all its contents.

Answer 3

While the steps you described seem inconsistent, the most likely cause is probably an inaccessible or missing profile. See the following documents for hints on this

• http://support.mozilla.org/en-US/kb/firefox-already-running-not-responding#w_check-the-profile-folder-name-and-location
• http://kb.mozillazine.org/Profile_in_use

I will update my answer with more details, when it becomes more clear, what you did exactly and which results you got.

Answer 4

What I experienced yesterday must be a major bug in Thunderbird. I've lost all of my mail. The folder for my corresponding profile is completely gone in C:\Users\username\AppData\Roaming\Thunderbird.

Answer 5

a Linux user here.

There is a possibility that the .thunderbird directory may have wrong permissions assigned so one may one to check that. I don't have any detailed idea how permissions work on Windows but on Linux my .default and .default-release directory had wrong permission and ownership. After I changed ownership from root to current user, my problem went away.

Also, assuming that Windows thunderbird profiles use similar structure as Linux, another reason maybe due to the existence multiple profiles directory (i.e. multiple instances of .default or .default-release directory) within the home folder of same user. In that case, one should keep only one instance of each directory that works and move the rest elsewhere.

I hope that helps.

Answer 6

@Meraj al Maksud 's answer remind me that I just receive a thunderbird's apt upgrade, which change my /etc/apparmor.d/usr.bin/thunderbird.

I put my profile in other directory and symlink ~/.thunderbird to it so my backup procedure would be easier. I modify the apparmor config to allow thunderbird read symlinked directory, so I have to modify the new apparmor again.

However I have not figure out how to update it now. I just remove the symlink and move the directory temporary

Answer 7

Uninstall and delete everything to do with thunderbird, then reinstall, worked for me, lost mail, but it's all on gmail anyway.

Answer 8

Download Revo Uninstaller and then uninstall Thunderbird with that. Then reinstall Thunderbird. Also use Win+E to start Explorer, then browse to C:\Users\your-username\AppData\Mozilla and delete the Thunderbird directory in there.

Oh, by the way, Windows has notoriously bad process management, so be careful not to mess with the operating system.