Millisecond Forums

Dear all,
I am using millisecond/inquisit 5 for a psychological experiment at our university. We always used to embed the experiment into a larger survey - the survey was hosted on SoSciSurvey, and then, via a html inline, we redirected participants to the experiment page. This worked fione for years, but suddenly, we get this and similar error messages on all browsers (not just firefox). I've checked whether it has anything to do with popup blockers or our firewall, but it doesn't. How can I make millisecond allow this embed?
Thanks in advance!