"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.

Solution 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?

Solution 2

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.

Solution 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.

Comments

[Paul]

I added your extra comment detail to the question. The path provided doesn't look right, Thunderbird is not in Mozilla normally. Where is the parent.lock file you deleted? And how were you able to end the task in task manager if the process wasn't running?

[Robert]

Will deleting my profile erase my email and configuration settings? What do I need to do to back that up first?

[Robert]

The problem looks more serious than expected. I do not see any Mail folder in my profile. I think I lost my email.

[Gurken Papst]

@Robert Yes, this would delete all your mail and settings so I cannot recommend these steps. Jonathan Reno should have put in a warning at least. The use of Revo Uninstaller is questionable also.