It is affecting all https sites you have tried ! Have you checked the time and date on the computer is correct ? More likely a firewall or other security related software is interfering.

• See Fix problems connecting to websites after updating Firefox
  • How to let Firefox use the internet on your Windows computer

See also Enable SSL to fix the Firefox cannot connect securely error message Secure connection failed and Firefox did not connect Secure Website Certificate

Thank you for your reply, John99. The date/time is fine, as is Windows Firewall. Firefox had been working just fine until the upgrade to 39.0 (from what version, I don't know). On restart after the upgrade, all https sites fail with Secure Connection Failed as stated.

Setting sites in security.tls.insecure_fallback_hosts does not help.

Hi kimalt, I am sure this must be something specific to your setup obviously I and the majority of users are not seeing this sort of problem. It's obviously not a site specific issue.

Did you try reseting the firewall by following the steps to remove, then add Firefox's setting again ?

• How to let Firefox use the internet on your Windows computer_configuring-windows-7-firewall

If that did not work lets take out as many other factors as possible.

1. Create a new additional Firefox profile for test purposes.
   • Profile Manager - Create, remove or switch Firefox profiles
2. Start Windows in Safe mode (Usually F8 key at boot time).
   • http://windows.microsoft.com/en-us/windows/start-computer-safe-mode#start-computer-safe-mode=windows-7
3. Temporarily Disable all Firefox plugins by setting to never activate in the addons manager.
   Firefox menu {Three bar icon) -> Add-ons {Jigsaw icon) -> |Plugins|
   • Disable or remove Add-ons
4. Restart Firefox in its own safemode. For instance hold Shift key whilst clicking on Firefox start icon. AND use the new profile.

Does that help ?

John99,

Thank you for your help on this issue. I went through everything you suggested to no avail (except the booting in safe mode). However, upon system reboot (again), Firefox suddenly and for no reason that I can ascertain decided to start working reasonably again.

Therefore the problem is solved, but I don't know why.

You're welcome. It's nice to know what happened where possible, but it works again, that is the important fact.

Thanks for posting back.

Same problem with 39.0

I can reboot and get it working as John99 said. But it doesn't last.

Everything worked fine until 39.0!!

Hi Mamapup, You would be better starting your own question and trying to follow the prompts to provide troubleshooting information.

I note you have already posted about crashes apparently related to your use of Norton. Hopefully that problem was resolved as you now state

Everything worked fine until 39.0!!

To post a new question please use /questions/new/desktop

If you post back again in this thread to confirm you have asked your own question we will be able to look for it.