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Can't start Firefox

charles42
charles42
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Out of the blue (I use Firefox 20 times a day) on Windows 10, I am getting an error message "Firefox is already running, but not responding. The old Firefox process must be closed to open a new window".

I close, but it keeps appearing. I went into Task Manager and end the task. After numerous tries, I (with lots of difficulty) uninstall Firefox. After I finally get it uninstalled (due to the same error happening during uninstall efforts) I upload the latest Firefox through Edge.

When I go to do the install, the error reappears. How can I get this to stop before I have to give up using firefox?

Out of the blue (I use Firefox 20 times a day) on Windows 10, I am getting an error message "Firefox is already running, but not responding. The old Firefox process must be closed to open a new window". I close, but it keeps appearing. I went into Task Manager and end the task. After numerous tries, I (with lots of difficulty) uninstall Firefox. After I finally get it uninstalled (due to the same error happening during uninstall efforts) I upload the latest Firefox through Edge. When I go to do the install, the error reappears. How can I get this to stop before I have to give up using firefox?

All Replies (1)

jscher2000 - Support Volunteer
jscher2000 - Support Volunteer
  • Top 10 Contributor
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Firefox usually unloads within 60 seconds after you exit out of it -- or displays the Mozilla Crash Reporter dialog, which allows you to end the program. If that fails, something unusual is going on.

In the Windows 10 Task Manager, could you click over to the "Details" tab. (If that tab is not visible, click "More details" to expand the dialog.)

On that tab, you can sort by name and see how many Firefox processes are running when you think there are zero. Are there any left?

If yes:

It's useful to add the "Command Line" column to see whether Firefox was run "headless" which is a trick malware sometimes uses. Right-click any existing column heading, then Select Columns, then check the box for Command Line and click OK. Anything unusual about the command line for the persistent process?

If no:

This could be caused by a lock file in your default Firefox profile. That's in the second section of this article: "Firefox is already running but is not responding" error - How to fix.