[_ck_]

If the new cookie has a different name, you should not be having a problem because bbpress should not even be looking at the old cookie?

You are getting a header error because you would have to put it at the very, very top of header.php before doctype – if that doesn’t work, you’d have to add it via a mini-plugin, put it into a file called function.php in your template folder

add_action('bb_send_headers','delete_old_cookie');

function delete_old_cookie() {

setcookie('wordpress_logged_in_REPLACEDcabef','',time()-3600);

}