[DrewM]

Originally Posted by Mystics

I don't know this hack...maybe you have to insert this code in one of the plugins/hooks added by the other hack:

$this->validfields['lastthreadprefix'] = array(TYPE_STR, REQ_NO);

No, maybe in a next version.
Re-upload includes/functions_threadprefix.php and check your global_start hook:

require_once(DIR . '/includes/functions_threadprefix.php');
if (THIS_SCRIPT == 'moderator' AND $_REQUEST['do'] == 'manageprefix')
{
	manage_thread_prefixes($foruminfo);
}

You can also try moving this code to the hook init_startup.

It's working with the extra plugin.