Why are you using a Very old version of Firefox?

FredMcD said

Why are you using a Very old version of Firefox?

I am not aware using an old version. Updates are automatically installed.

I am not aware using an old version. Updates are automatically installed.

System Details Windows 7 Firefox 33.0

Type about:support in the address bar and press Enter. Under the main banner, press the button; Copy Text To Clipboard.. Now in the Reply Box on the forum page, do a right-click in the box and select Paste.

This will show us your system details. No Personal Information Is Collected.

Toepassingsbasics

Naam: Firefox Versie: 55.0.3 Build-ID: 20170824053622 Updatekanaal: release Useragent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:33.0) Gecko/20100101 Firefox/33.0 OS: Windows_NT 10.0 Multiprocess-vensters: 0/1 (Uitgeschakeld door toegankelijkheidshulpmiddelen) Web Content Processes: Google-sleutel: Gevonden Mozilla-locatieservicesleutel: Gevonden Veilige modus: false

olthofh said

Useragent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:33.0) Gecko/20100101 Firefox/33.0 OS: Windows_NT 10.0

https://support.mozilla.org/en-US/kb/how-reset-default-user-agent-firefox

http://www.howtogeek.com/113439/how-to-change-your-browsers-user-agent-without-installing-any-extensions/

I have done what you suggested (resetted the user-agent to default except dom.push.userAgentID) but it didn't work. I still always get the same message.

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Do a clean reinstall of the current Firefox release and delete the Firefox program folder before installing a fresh copy of the current Firefox release.

• download the Firefox installer and save the file to the desktop
  *https://www.mozilla.org/en-US/firefox/all/

If possible uninstall your current Firefox version to cleanup the Windows Registry and settings in security software.

• do NOT remove "personal data" when you uninstall the current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• (64 bit Firefox) "C:\Program Files\Mozilla Firefox\"
• (32 bit Firefox) "C:\Program Files (x86)\Mozilla Firefox\"

• it is important to delete the Firefox program folder to remove all the files and make sure there are no problems with files that were leftover after uninstalling
• http://kb.mozillazine.org/Uninstalling_Firefox

Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you uninstall and reinstall or update Firefox, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

If you keep having problems then you can create a new profile to test if your current profile is causing the problem.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

olthofh said

I still always get the same message.

This is often caused by anti-virus or security software such as Kaspersky, Avast, ESET or Bitdefender. If you have such software installed, would you please disable it and see if that will make a difference  ?

I tried everything you advised except disabeling my security software. That is Bitdefender, I don't know how to do that. Until now no result. Installing in Thunderbird was no problem.

When you go to Windows Control Panel => Programs Do you see Bitdefender there  ? If so : click on 'Uninstall'

If you don't want to remove Bitdefender, but only disable it, you could contact them : https://www.bitdefender.com/support/contact-us.html?last_page=1849

But : with Windows Defender and the safest browser on the planet - who needs Bitdefender (known to cause problems .... )

The problem is solved at last. I deleted Firefox and installed a fresh copy. I did it yesterday and it seemed there was no result. However today, after starting up my pc, I tried to install Sticky Password again and then it worked out well. Thank you all for your help.