CoursePress Pro: Blank Screen on Unit Page

Hi--
I'm having trouble with CoursePress Pro + PageLines. I'm using PageLines to design the theme, and so far, it's working great with the WPMUDEV plugins I'm using. However, I've run into a problem with CoursePress Pro.

While the assignment and introduction (first unit) appear to be working, when I use a video unit, I get a blank page in both Firefox and Safari. However, it appears to be working in Chrome.

Any guesses as to what could be causing this?