Try to disable IPv6 (check for other possible causes as well). *https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can You can check for issues with Total Cookie Protection. *https://support.mozilla.org/en-US/kb/total-cookie-protection-and-website-breakage-faq *https://support.mozilla.org/en-US/kb/introducing-total-cookie-protection-standard-mode Are you using a proxy or VPN? You can check the connection settings. *Settings -> General -> Network: Connection -> Settings If you do not need to use a proxy to connect to internet, select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly. See "Firefox connection settings": *https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors *https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can *https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

Thanks for the information on what might be causing the problem. I tried several of the items you suggested but they did not solve the problem. In the end, it turns out that I was missing an Norton AV program update. Once I applied the update, the problem was resolved. FYI - the initial problem only occurred with Firefox. Problem did not occur with Microsoft Edge. Thanks for your help!