Happy112 said

Would you consider posting this on the Microsoft support forum   ? (It's pretty similar to this forum) https://answers.microsoft.com/en-US/windows/forum/windows_10 Or the Dutch section : https://answers.microsoft.com/nl-nl/site/startsignin

Thanks, but I won't.

As the BEX error message is from Microsoft posting on a MS forum to ask about it could have been a good idea.

I did ask earlier in this thread: In Fx54 did you try in Firefox's safe mode and Windows safe mode at the same time. Did you still see the problem then ?

Other than trying to avoid the issue by using SafeModes and considering more fully the possibility it could be a malware related problem I do not see any way forward with this.

• Others do not seem to be able to reproduce this. If others are not seeing the issue then probably no one is working on trying to find and fix the problem.
• As the error is coming up only at closedown of Firefox it is going to be hard to get any information from Firefox about this.

I do note that you tested in Firefox's safe mode and still see the issue but If the issue goes away in one or both of the safe modes at least it gives clues as to possible culprits.

As you see an issue that most people do not then there is a possibility that something is modifying or corrupting the Firefox program files. If you do a clean install of Firefox involving deletion of the program files it may help and is certainly something to try. I would suggest you actually do that clean install whilst in Windows safe mode as it may increase the chances of successfully doing a proper clean reinstall.

Clean Reinstall

Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location.

To do a clean reinstall of Firefox, please follow these steps: Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from mozilla.org (or choose the download for your operating system and language from this page) and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (or open the Firefox menu and click the close button ).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be easily recovered unless they have been backed up to an external device! See Back up and restore information in Firefox profiles.

Please report back to say if this helped you!

Thank you.

john99, I appreciate your help but some of the things you propose are too laborious. Of course I can try double safe mode and see what happens, and maybe the error doesn't occur. And than what? That wouldn't solve the problem.

This is not why I came here. I want to hear/read from some Firefox rep what IS the cause of this. Till now no one can tell me where this originates. I know one thing for sure: all was well till FF54. No changes or updates were made to Windows in between FF53 working well and FF54 going bad. Ergo...

IF anyone would be able to convince me that not Firefox but Windows is the cause, THEN maybe I will post a question on MS. I say 'maybe', because I've been there a few times before and it's the same story all over: a plethora of suggestions and could be's. That's the problem with these nowadays 'support' fora: users are left to solve eachother's problems that actually should be solved (or at least explained) by the manufacturer itself.

Thanks you all

wwwaste said

I want to hear/read from some Firefox rep what IS the cause of this. Till now no one can tell me where this originates. I know one thing for sure: all was well till FF54. No changes or updates were made to Windows in between FF53 working well and FF54 going bad.

There are thousands of change in each major release, so unless numerous people report the same problem with a range of clues, it can be difficult to triangulate.

There is a process known as regression testing to track down which exact change causes a problem. It works best when the problem is quickly and easily reproduced, but it's still rather laborious. More info: http://mozilla.github.io/mozregression/

wwwaste said

IF anyone would be able to convince me that not Firefox but Windows is the cause, THEN maybe I will post a question on MS.

You yourself said that you thought that this might not be caused by   Firefox,   but by   Windows   (see your second post in this thread). The message comes from   Windows   .........