OpenDNS could be keeping the security certificates from working, but that’s not the first thing that I would look at in your scenario.
Does this happen on all of the https sites that you visit? Or just a few? Maybe even just one? It’s possible that there really is a certificate error on the server; perhaps something as simple as an expired certificate could cause this error message to appear. If so, that’s a server issue and not yours.
On the other hand, if you’re seeing this message at all https sites, then it could mean a couple of different things.