That issue can be caused by corrupted cookies. *https://support.mozilla.org/kb/Cannot+log+in+to+websites Clear the cache and the cookies from sites that cause problems. "Clear the Cache": *Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now" "Remove Cookies" from sites causing problems: *Tools > Options > Privacy > Cookies: "Show Cookies" Start Firefox in <u>[[Safe Mode]]</u> to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes). *Don't make any changes on the Safe mode start window. *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes ---- See also: *https://support.mozilla.org/kb/make-firefox-remember-usernames-and-passwords *https://support.mozilla.org/kb/Username+and+password+not+remembered