[Plugin: Attachments] (v1.5.3.2) Attach button mising from file upload dialog on custom post type

Recently updated to 1.5.3.2, now when users are attaching a new file the ‘Attach’ button is missing from the uploaded file details form. The button is visible if you go via the media library tab and attach an existing file.

This is a new development as the site has been using this plugin for a while now and my users have only just noticed the button is missing when uploading a new file.

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