I have recently had the dreaded "This connection is untrusted" message and then it got worse by not offering me the opportunity to go to the site, regardless. This got worse and worse, until finally I couldn't go to any https:// site whatsoever, including mail.yahoo.com, duckduckgo.com, etc. I read all of the links and did all of the searches. I synchronized my time and date. I uninstalled and reinstalled Firefox. I back-dated firefox to version 13. I beta-updated to 32 (or whatever the most recent beta release is). I went into about:config and changed everything even remotely possible. I did the options route and removed all custom exceptions. I added additional exceptions. I tried safe mode. I tried disabling all plugins and add-ons manually. Finally, I found the solution that worked for me. I have Kaspersky Internet Security on my machine. At some point, I must have enabled Kaspersky to check all https connections. Goto to Kaspersky Internet Security. Click on Settings, Additional, Network settings, DE-select "Scan Encrypted Connections." Everything is now back to normal. If you're using Kaspersky Internet Security (I have build 14.0.0.4651(h)) and you are having this annoying problem, try this fix. Sorry I couldn't reply to other threads where this problem was posted, because I didn't have an account, and you can't sign up to answer, only to ask. Therefore, I'm "asking" the solution I found to this problem.