There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connections and send their own certificate. 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 https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message https://support.mozilla.org/en-US/kb/connection-untrusted-error-message http://kb.mozillazine.org/Error_loading_websites

Note that the OP is on the Linux platform, so no need to post instructions for Windows. CBC can only be accessed via an open HTTP connection, so I don't think this has anything to do with SSL. Did you send crash reports for those crashes? *https://support.mozilla.org/en-US/kb/Mozilla+Crash+Reporter