There's been a couple of times now while visiting the forums I've gotten the message "This Connection is Untrusted" and warning me of possible security issues. Both times this has happened when I clicked a link to another page on the forums (for example, clicking a link to someone's "Absences" thread, listed in their signature), which opened in a new tab of my browser.
I'm not sure what this is about but thought it was rather odd. I thought I'd mention it, just in case. I'm using Firefox in Windows XP, if that makes a difference.