On two machines, one running Windows 7, one with Windows 8. (The biggest problem is with the Windows7 machine) One day everything was fine, the next, websites such as Facebook, Google, Yahoo Mail, etc., anything with a HTTPS will not load. I get the warning page that the site could be fraudulent due to to an invalid certificate. "sec_error_unknown_issuer" is a common error. Some sites will offer up a "I understand the risks" option, most wont. Even the ones that allow me to try and bypass still won't load properly. We have not installed any new software or virus protection on either machine. The only change that has been made was a new wireless network was added and name changed. (This has happened before with no ill effects) Any suggestions?