Index: wp-admin/includes/media.php
===================================================================
--- wp-admin/includes/media.php	(revision 11233)
+++ wp-admin/includes/media.php	(working copy)
@@ -478,7 +478,7 @@
 		$return = media_upload_form_handler();
 
 		if ( is_string($return) )
-			return $return;
+			return wp_iframe( 'media_upload_gallery_form', $return );
 		if ( is_array($return) )
 			$errors = $return;
 	}