But that error is not from *your* system - it is coming from *their* server - see that top line where it says Microsoft Active Directory Certificate Server?
AFAICT, that is the error message being generated from their end.
However, there is one thing to note - are you using IE? If so, is IE in protected mode for this site? If so, then add this site to your trusted sites list and see if it works then....
To do that, go to the site, then try to log in. You should change to a secure page, using an HTTPS address.
Then click on Tools --> Internet Options --> Security tab --> Trusted Sites --> Sites button - in the box that opens up, you should already have your site listed, simply click the Add button. after that, close IE then reload IE and see if it works.
If you need screen shots or a more guided help, let me know.