Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions (Firefox menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem. *Switch to the DEFAULT theme: Firefox menu button/Tools > Add-ons > Appearance *Do NOT click the Reset button on the Safe Mode start window *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes ---- It is possible that your firewall or other security software blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program. Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access to install for Firefox and the plugin-container process and the updater process. See: *https://support.mozilla.org/kb/Server+not+found *https://support.mozilla.org/kb/Firewalls *https://support.mozilla.org/kb/fix-problems-connecting-websites-after-updating