Can't access Google

I'm using Firefox 40.03 with Win 7 Pro and I keep getting the following error whenever I try using Google:

"You have asked Firefox to connect securely to Google, but we can't confirm that your connection is secure.

Normally, when you try to connect securely, sites will present trusted identification to prove that you are going to the right place. However, this site's identity can't be verified.
What Should I Do?

If you usually connect to this site without problems, this error could mean that someone is trying to impersonate the site, and you shouldn't continue.

This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox only connect to it securely. As a result, it is not possible to add an exception for this certificate."


Get the same result whenever I try adding FF addons as well. Anyone know the solution this this?