Pop-up plugin Appears Underneath Embedded Video in IE

Hi WPMUDev!

I have your PopUp Pro plugin installed on DrNorthrup.com (set to appear on homepage 60% down the page). You guys really have a great product here. The flexibility and range of settings that it comes with out-of-the-box are quite extensive, and it's been a pleasure to work with so far!

The problem I'm writing about is that in the latest version of Internet Explorer, the pop-up appears underneath the embedded YouTube video (see screenshot). At first I thought it might be a z-index issue, but I see that the pop-up's z-index is set to 100000, and the video doesn't appear to have a z-index set. Could you please offer any ideas on how to fix this?

Thank you,
Kathryn