The solution is here: http://forum.ait-pro.com/forums/topic/bbpress-sending-a-topic-to-trash-gives-403/#post-6442
You need to add a wp-admin skip/bypass rule for the post.php file.
The solution is here: http://forum.ait-pro.com/forums/topic/bbpress-sending-a-topic-to-trash-gives-403/#post-6442
You need to add a wp-admin skip/bypass rule for the post.php file.