Yes, I have tried starting Firefox in safe mode.

Thank you for your response.

No errors in the event viewer. I did uninstall Firefox by manually removing the directories, but not the registry entries. I have Firefox as my default browser. ...

Thank you for your response. The Firefox icon does not appear on the taskbar.

I have been unsuccessful updating two machines to Windows 10 1607. During my latest attempt Firefox would not display its browser screen. If I looked at task manager I could see firefox32* loaded. ...