Hi, Please : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 59.0 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

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

I contacted my internet provider and the remotely rebooted the modem and that took care of the problem. Thank you for your help.

Bob

puffrbelly said

I contacted my internet provider and the remotely rebooted the modem and that took care of the problem. Thank you for your help. Bob

Hi, glad is fixed, please select Your Answer as the Solution so others may find it.

I've been fighting this issue as well for over a week now. Thought it was a firewall issue, a LAN connection setting, but turns out it was an AVAST antivirus problem.

Searching through dozens of threads...someone mentioned a setting in AVAST. When I tried opening AVAST dashboard, it would never pop up. I tried uninstalling it, but would not uninstall. Finally had to download their uninstall tool called AVASTCLEAN.

Ran that utility in Windows10 safe mode, rebooted, ran CCleaner, then opened Firefox.

FIXED!!!

Hope this helps someone...

DrCyKosis said

I've been fighting this issue as well for over a week now. Thought it was a firewall issue, a LAN connection setting, but turns out it was an AVAST antivirus problem. Searching through dozens of threads...someone mentioned a setting in AVAST. When I tried opening AVAST dashboard, it would never pop up. I tried uninstalling it, but would not uninstall. Finally had to download their uninstall tool called AVASTCLEAN. Ran that utility in Windows10 safe mode, rebooted, ran CCleaner, then opened Firefox. FIXED!!! Hope this helps someone...

Thanks for letting us know.

Or to mark this as Helpful as you already marked it as solved.

DrCyKosis, is not the thread starter.

I get the TLS Handshake lockout then it times out with messages like the one shown in the attached image (note the site). I get the same type of message when trying for Mozilla Support too! I assume both messages are incorrect! I am using Kaspersky so none of the answers about Avast apply. I removed Firefox and re-installed. The fault is 'intermittent' but happens too many times to be ignored.

Hi whitehairedgeezer2

See:

• https://support.mozilla.org/en-US/kb/troubleshoot-SEC_ERROR_UNKNOWN_ISSUER

Thanks Cor-el. Tried the document linked here. Made no difference - switched off my AV completely; removed and reinstalled my AV (Kaspersky Free); switched off my firewall; switched off IPV6; changed DNS from automatic to 8.8.8.8; removed Firefox and old profile and reinstalled Firefox; switched off tracking and back on again.; installed latest version W10; persuaded isp to supply new router. No change. Sometimes wont load my startpage. Often F5 key will allow pages to load. Often page continues to load with dot circling in tab and message about waiting for data from site. Shut tab and click linkagain will often load page properly. Sometimes pages time out (google and Mozilla being 2 I noticed particularly) All drivers upto date. Thunderbird works perfectly.

@whitehairedgeezer2...

Just throwing this out to help isolate your issue. Do you have another account on your machine you can login with? Or could you create a test account?

If so, try that account. If it works...then the issue is your local profile, and could be some underlying security setting in the registry.

This step would at least point to a broken local profile, or a Firefox issue.

Hope this helps...

I have the same problem, but I find it's not just limited to Firefox, it can occur on three other browers I tried. It appears to be an ISP problem.

My ISP just sent me another router (3rd one) which is a bit higher spec thatn the last one. Everything seems to be ok now.