Please Update to the latest Firefox 15.0.1 version.

• Help > About Firefox

The Firefox 12 version that you currently run is no longer supported with security updates

Does that only happen with Gmail?

Check the date and time in the clock on your computer: (double) click the clock icon on the Windows Taskbar.

• https://support.mozilla.org/kb/Secure+Connection+Failed

Clear the cache and the cookies from sites that cause problems.

"Clear the Cache":

• Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Tools > Options > Privacy > Cookies: "Show Cookies"

You can also try to rename the cert8.db file in the Firefox profile folder to cert8.db.old or delete the cert8.db file to remove intermediate certificates that Firefox has stored.
If that helped to solve the problem then you can remove the renamed cert8.db.old file.
Otherwise you can rename (or copy) the cert8.db.old file to cert8.db to restore the previous intermediate certificates.
Firefox will automatically store intermediate certificates when you visit websites that send such a certificate.

Can somebody help. I have followed the instructions mentioned... cleaning the cookies and change / rename the cert8.db. but after i can get in to gmail.com... suddenly after a few minutes, the status changed again to untrusted connections. so i have to do again the above mentions steps.. again and again.. this thing drive me crazy.. Is there any perfect solution to this problem?

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.

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

What next? i still can not go in.

Hi Cor el... thanks for the advice, but the problem remain happening.. i could go in for several minutes and then the status back to untrusted.

Hi Cor El, need your help.. same things happen, i cannot access gmail. the certificate when were viewed said that google certificate is not trusted.

I don't know what to do ... even when i click confirm to add exceptions, i could see the front page of the gmail.com, but still cannot go in.

Did you click the View button to inspect the certificate and looked at the details to see who issued the certificate?

Your first screenshot doesn't show the technical details that usually gives a clue.

Dear Cor El,

pls find below the screen shoot of the certificate. up to now the problem were still appear and i could not access my gmail.com

Hi Cor El,

Can you help me? i still cannot go to gmail.com or other google services.

Your screenshot doesn't show who issued this certificate and other details clearly, so I can't tell what is wrong and why there isn't a certificate chain build.