hi, next to the security software already in place, please run a scan with various other security tools like the free version of malwarebytes, adwcleaner & eset online one-time scanner.

Thank you for the suggestion but unfortunately, even after baidu, eset and malwarebytes were done (and did remove some potentially infected files) I reinstalled the current version of Firefox and received the exact same error message. Then I rebooted the machine (off-line with no internet connection). Firefox then gave me the exact same error message.

Other thoughts???? Thanks, in advance.

Please uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved.

Then install from a fresh full version installer https://www.mozilla.org/en-US/firefox/organizations/all/

You can try and repair any Registry Issues doing this : To run the SFC command use the Windows key + X keyboard shortcut to open the Power User menu and select Command Prompt (Admin). Type "SFC /SCANNOW" (without quotes or copy/paste) and press Enter. For more information on using SFC, please refer to the Microsoft KB: Use the System File Checker tool to repair missing or corrupted system files

Note : SFC fixes files locally using files found on your system.

Please let us know if this solved your issue or if need further assistance.

I did all these things, repeatedly, rebooting or turning the machine off between "cycles". One anomaly: when I run diskcleanup, it does not offer any option to "Cleanup System Files" no matter how many times I run it, back to back or with a reboot in between. I did run the SystemRestore option to no avail.

I've run the defragmenter, and every other utility that I can think of to clear caches. Sorry to have to keep asking for help but I really miss having Firefox on my old machine.

Please advise what else I might try. Again, with thanks.

Try Repair System Registry and Files

(FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN)

To run the SFC command use the Windows key + X keyboard shortcut to open the Power User menu and select Command Prompt (Admin). Type "SFC /SCANNOW" (without quotes or copy/paste) and press Enter. For more information on using SFC, please refer to the Microsoft KB: Use the System File Checker tool to repair missing or corrupted system files

then reboot.

Please let us know if this solved your issue or if need further assistance.

Try to disable accessibility services in Firefox.

• Options/Preferences -> Privacy & Security -> Prevent accessibility services from accessing your browser
• https://support.mozilla.org/en-US/kb/accessibility-services