Yes, this is an author blog, but I also love computers, and I love fixing them. So I hope you've found this post because you're tired of all the other posts telling you to fix your clock or date and time if you get an error message saying "This Connection is Untrusted" after you've reset your browser. But guess what, it's most likely not the stupid clock that's wrong. It's your flash plugin. After you reset your firefox back to square one, it lost all the previous flash updates you'd added to it. I had this problem for a whole day before I realized how to fix it. And it's simple. Just update your Adobe Flash.
You should be able to get to your flash files from the lower right of your computer, near the clock (Sorry, Mac users, I'm on a PC). If they're not there, and you can't figure out where your flash files are, just turn your computer off and on. A box should pop up once you restart telling you to update your flash files. Click Update and everything should be good to go after that.
Hope this helps.