Who is the issuer of the certificate?

Check out why the site is untrusted (click "Technical Details to expand that section) and if this is caused by a missing intermediate certificate then see if you can install this intermediate certificate from another source.

You can retrieve the certificate and check details like who issued certificates and expiration dates of certificates.

• Click the link at the bottom of the error page: "I Understand the Risks"

Let Firefox retrieve the certificate: "Add Exception" -> "Get Certificate".

• Click the "View..." button and inspect the certificate and check who is the issuer of the certificate.

You can see more Details like intermediate certificates that are used in the Details pane.

If "I Understand the Risks" is missing then this page may be opened in an (i)frame and in that case try the right-click context menu and use "This Frame: Open Frame in New Tab".

Note that some firewalls monitor secure (https) connections and send their own certificate instead of the website's certificate.

Do a malware check with some malware scanning programs on the Windows computer.
Please scan with all programs because each program detects different malware.
All these programs have free versions.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender: Home Page:
  http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

Cor El - I have completed all of the scans and attempted to access google again, but am still receiving the warning. I am unfamiliar with certificates and their sources and how to repair this. Can you provide further details?

Did you do the steps I posted above to retrieve (I understand the risk) and view (inspect) the certificate and check how issued the certificate?

That should give a clue of what is wrong.

finally exhausted all the remedies that have been outlined. Followed all of the steps you described. I am posting this as a potential fix for others that are suffering the same problem. I called Microsoft tech support today and they went through my registry and deleted all of the malware and virus scan software. They said that having so many different malware scanning programs running simultaneously provided a great potential for conflict. They also ran a scan program Hitman pro 3.7.8 and discovered several malware programs that went undetected by all of the other scans. they then cleaned up my registry, They told me that the latest version of IE (11) was not compatible with Windows 7 and unistalled. I then told them that a program was still in my registry that i was suspicious of named Browsersafeguard and asked them to remove it. When they unistalled it, it referenced the above certificate and when completely removed, my system has been restored. This program resided only my my user account and no others.I have to download another scanning program this evening that will scan more comprehensively and the Microsoft tech said will make certain that all issues are resolved. Didn't want to pay the money for support but they did get me back on track, so it's money well spent.