Hello Elliot,
I am experiencing similar problem with ACF 4.2.2 (Option page 1.2.0) right now. When I deactivate Formidable 1.07.01 the problem is gone. The problem is only for Options page and for WYSIWYG link button.
Uncaught TypeError: Object [object Object] has no method 'wpdialog'
in the wp-includes/js/tinymce/wp-tinymce.php line 24