Sorry about the phone number chase, you're in the right place now I think.

Does the error page let you view the certificate? I have attached screen shots of the certificate information I get for the site. If you compare, is yours the same or different?

If you can't view the certificate in Firefox, can you view it in IE?

check your date and time on your computer... site certificates are date and time stamp sensitive...if your sysetm is not keeping time correctly then you need to check your modem or router to ensure it is updating from a reliable time centre...also the battery on your motherboard may have failed and is resetting the mobo to its manufacture date instead of the correct date and time

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.

If that didn't help then remove or rename secmod.db (secmod.db.old) as well.

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder