"Your vision will become clear only when you can look into your own heart.
Who looks outside, dreams; who looks inside, awakens."
-Dr. Carl Jung
Well, if you wish to use Firefox, for the time being I suggest accessing the site without a security certifice (http:), however once the issue(s) is/are resolved, you can go back to using a secure connection. It isn't a browser problem, true, it's an issue with the security certificate for the site. They should be working on it, but for the time being you should use a non-secure connection to the site.