Adding or Editing a Subscription - Find User Popup doesn't work

Hello,

I am trying to edit or add a subscription for a user and when I click on the User* field to select one, the popup emerges, but it does not allow for interaction. Instead it shows up behind an opacity of .8 and when I click anywhere it just closes the popup.

Here's a video: http://screencast.com/t/IsZSkWFs

Thank you for you assistance.

Dawn