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How do I get rid of Configuration Error dialog box stating, "Failed to read the configuration file. Please contact your system administrator."

Jason Alsin
Jason Alsin
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After a recent beta version installed, my profile seems to have a corrupt configuration file. But I don't know how to figure out which one. It only happens on my Windows 10 laptop. My profile syncs with another Windows 10 laptop, 2 user accounts on a Linux Mint desktop, and an LG phone. I followed the support article and changed the settings so that I was only on the release channel, rather than the Beta channel. I tried the Refresh Firefox. After resyncing my profile, the error returned. I uninstalled the newer Beta release, completely deleted the User/AppData/Roaming/Mozilla folder. I reinstalled the current release (72.0.2). After resyncing my profile, the error still returned. Every time I start Firefox, I get the annoyance of the error dialog box. After clicking OK, Firefox opens and works perfectly fine. How do I find which file in my profile is causing the error on just one computer?

After a recent beta version installed, my profile seems to have a corrupt configuration file. But I don't know how to figure out which one. It only happens on my Windows 10 laptop. My profile syncs with another Windows 10 laptop, 2 user accounts on a Linux Mint desktop, and an LG phone. I followed the support article and changed the settings so that I was only on the release channel, rather than the Beta channel. I tried the Refresh Firefox. After resyncing my profile, the error returned. I uninstalled the newer Beta release, completely deleted the User/AppData/Roaming/Mozilla folder. I reinstalled the current release (72.0.2). After resyncing my profile, the error still returned. Every time I start Firefox, I get the annoyance of the error dialog box. After clicking OK, Firefox opens and works perfectly fine. How do I find which file in my profile is causing the error on just one computer?

All Replies (1)

jscher2000 - Support Volunteer
jscher2000 - Support Volunteer
  • Top 10 Contributor
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Hi Jason, one of the things often included with Sync are add-ons. So with that in mind:

Could you test in Firefox's Safe Mode? In its Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.)

If Firefox is running: You can restart Firefox in Safe Mode using either:

  • "3-bar" menu button > "?" Help button > Restart with Add-ons Disabled
  • (menu bar) Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

That error message also can arise when there is a problem with a local configuration file, although I am not aware that Sync could copy it over. To investigate:

Check for alien script files in your Firefox program folder as follows. Those are nearly always in one of these locations (varies for 32-bit / 64-bit):

  • C:\Program Files\Mozilla Firefox\defaults\pref
  • C:\Program Files (x86)\Mozilla Firefox\defaults\pref

Caution: Do not double-click script files! The default action for a script file it to execute as a Windows system script. (Typically this would just not work, but why risk it.)

Make sure Windows is showing hidden files: https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

It's also a good idea to turn on display of all file extensions: https://www.bleepingcomputer.com/tutorials/how-to-show-file-extensions-in-windows/

A file named channel-prefs.js is normal. Any other file in this folder is suspicious and could be used to modify Firefox behavior. Remove any such files to a neutral location for further analysis at your leisure. You can rename the file with a .txt extension and examine it for the name of another file that contains the locking code.