Does the program open, but then closes, or does it do nothing?

Start your Computer in safe mode with network support. Then start Firefox.
Try Secure websites. Is the problem still there?

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode
Starting Any Computer In Safe Mode; Free Online Encyclopedia

Mister Fred, thnx for your answer. The programs Firebird and Mozilla don’t start. I think after updating Win10 (to version 2004). I hear someting silently clicking internal in my hp laptop, but nothing more. But Now and then, after several tryes suddenly the programs start, but only after a long wait.

I tryed safe mode start. My screen was ‘strange’ but both Firebird and Mozilla started, but i had no wifi Connexion.

What do you think? Maybe a temporary bug in windows?

Greatings Wilfried Prenen

Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

Dear mister Fred nothing solves my problem. I think something happend when i downloded the update Win10 2040 or an update from Firefox and thunderbird.

To begin, a have no problems with other programs, but When I click on the icons from firefox and/or Thunderbird these programs don't start....most of the times...now and then the do start. Very strange. I hope that it is an update problem on this laptop. My other laptop has nog problem with these programs.

thnx wilfried Belgium