Every time I try to log into ANY website that is secured, I get an error message "This connection is untrusted."

Question

The error message is:
This Connection is Untrusted
You have asked Firefox to connect securely to www.facebook.com, 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.
www.facebook.com uses an invalid security certificate. The certificate is not trusted because no issuer chain was provided. (Error code: sec_error_unknown_issuer)
If you understand what's going on, you can tell Firefox to start trusting this site's identification. Even if you trust the site, this error could mean that someone is tampering with your connection.
Don't add an exception unless you know there's a good reason why this site doesn't use trusted identification.
Steps I have take so far:
Verified that system clock is correct
Cleared all cache, history, cookies, etc.; didn't help
Started Firefox in Safe Mode; didn't help
Disabled all Firefox extensions; didn't help
uninstalled and reinstalled Firefox using Control Panel; didn't help
Ran Microsoft Safety Scan for malware; nothing was found
Other information:
This problem exists ONLY in my user profile and ONLY in Firefox. All 5 other users can run Firefox with no problem. I can run IE and Chrome with no problem.
Problem exists in ALL secured (https) sites.
I use Avast and Windows Firewall. Had never heard of ESET or BitDefender before searching these forums.
A lot of the sites don't give me the option to Make an Exception. The two that I tried to make exceptions for, still wouldn't open.
Run Windows 7 64-bit

Answer 1

unfortunately the fiddler2 issuer in certificates might be a sign of unwanted software present on your pc that is intercepting secure network traffic. please go into the system control panel and uninstall programs like BrowserSafeguard, BrowserSafe, SafeGuard or other software that sounds suspicious and didn't get installed by you intentionally.
<br>_{reference: https://support.mozilla.org/en-US/questions/982532#answer-520145}
afterwards, run a full scan of your system with different security tools like the [http://www.malwarebytes.org/products/malwarebytes_free free version of malwarebytes] & [http://www.bleepingcomputer.com/download/adwcleaner/ adwcleaner].
[[Troubleshoot Firefox issues caused by malware]]