@Patrick Steil - After seeing the screencast, the 500 isn't the only issue I noticed.
That entire top section "Creative Commons" etc does not belong on that page. It has nothing to do with popup maker.
But the WSOD is generally a fatal php error. It should be logged in your servers error logs if you have access.
If I had to guess another plugin is colliding for some reason. Though it often tends to be the themes that take too much liberty in the admin and break things.
If you can get the error we can tack down the issue. Hard to know without that error message or knowing which plugin/theme is causing the conflict so I can duplicate.