Click on "Display" tab -> "Invalid post type" frm_display

I recently updated from Formidable v1.06.05 to v1.06.08 (free version) and have a found a consistent error. When editing a form, if I click on the “Displays” tab, WordPress goes to a screen that’s blank except for the words “Invalid post type”.
I see that the link associated with the Displays tab changed between v1.06.05 and 1.06.06. This is logged in Changeset 604316 as a change in the classes/views/shared/form-nav.php file. If I manually change the link back to the way it was in v1.06.05 using FireBug, I seem to get the correct action (i.e. no error).
Anyone know if frm_display is supposed to have been entered as a post type during the plugin update, or is the change from admin.php to edit.php in that link the culprit? What’s a good way to fix it?

http://wordpress.org/extend/plugins/formidable/