No profile drop-downs in contribution page edit mode.

Since upgrading to Civi 4.5.x, I have lost the drop-down options in contribution page edit mode. So I am no able to select which profile(s) to include in the contribution page. My internal team of developers believe there is some new javascript backbone that has been introduced in 4.5.x that is causing this, but we have not being able to nail the culprit.

This is CiviCRM 4.5.2 installation on the latest stable Wordpress.