First, beforehand: we don't support alternating between Firefox
3.6 and TenFourFox, and with TenFourFox 38 you run the real
likelihood of losing data. You do so at your own risk.
That said, assuming you are running TenFourFox 38, we use the
exact same certificate store as regular mainline Firefox, so you
should never see that message. I'd check your computer's clock.
Even being off by just a few minutes can be enough to make
certificate checks fail, and some users haven't noticed their
calendars were off by years.
I have this problem, too. It totally disables tenfourfoxbox (which has worked perfectly with this website since forever), yet I can open the same website with firefox 38.10.0. The problem is that I absolutely need it to work with tenfourfoxbox. This problem began one week ago; until then, tenfourfoxbox worked perfectly with this website.
Additionally, it is happening on four different computers.
My date and time are absolutely correct as they are set automatically.