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.
Check your clock
First, check your computer’s clock, the one that appears on your screen. Make certain that the year, date, time, time zone and daylight saving time (or “summer time”) settings are all set correctly.
When your computer checks the accuracy of a certificate part of that involves the current time. If your clock is off, then your machine may assume that there’s something wrong with the certificate. If the clock is off, every https certificate in the world might look broken when you access it.
Try different browsers
Next, I would fire up a different browser on any of your other machines and see if you see the same problem.
If you don’t have any other browsers, go download, install, and then open Firefox1 to see if it displays the same warning. I don’t know if this will provide you with a solution, but it’s a quick and easy way to eliminate Internet Explorer-specific issues.
Now, OpenDNS could be the culprit, but to be honest, I have a hard time envisioning exactly how that would happen. However, I would certainly see if it works without OpenDNS configured.
Change the DNS settings either on your router or a specific machine to use Google’s public DNS, your ISP, or any other set of DNS providers. (Be sure and flush your browser’s cache after changing DNS as well.) My guess is the problem won’t necessarily go away. In that case, it’s probably not an OpenDNS issue.
It could be malware. I hate to throw that out there, but some form of malware could be interfering with how you visit certain sites. If those sites are affected or use https, then the malware could be trying to steer you wrong. So, as always, make sure you scan with updated anti-virus and anti-spyware software and your anti-malware tools are up and running properly.
If the problem is on the server side…
If you’re seeing this across a family of sites or just one site, then it’s likely that it’s actually a problem on the server’s side.
The last point that I’ll throw out here is that the error message itself usually has a lot of important information that would help diagnose exactly what’s going on. If that’s the case, I’d strongly recommend that you include the entire text of the error that comes up when you have a problem accessing a secure site and there’s some kind of a certificate problem.