Planet CakePHP

My knowledge level here is like zilch, but please bear with me.

I have a site built in PHP/MySQL that uses the Smarty template engine. There's a registration form that, for some reason, isn't posting the data to the DB. Here's the function:

        $u = new H_User;
            $u->setFrom($p);
            $smarty->assign('user', $u);
            $val = $u->validate();
            if ($val === true) {

                $temp = new H_User;
                $temp->orderBy('user_id desc');
                $temp->find(true);

                $next_id = $temp->user_id + 1;

                $u->user_id = $next_id;
                $u->user_password = md5($p['user_password']);
                $u->user_regdate = mktime();
                $u->user_active = 0;
                $u->insert();
                $hash = md5($u->user_email . $u->user_regdate);

                $smarty->assign('hash', $hash);
                $smarty->assign('user', $u);

                $smarty->assign('registration_complete', true);

                $d = new H_Demographic;
                $d->setFrom($p);
                $d->insert();

How can I figure out what's wrong here? I don't get any PHP errors and I don't know how to get MySQL to display the errors that might indicate what's wrong with that syntax.

MORE INFO AS PER REQUESTS

#
# Table structure for table `user`
#

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `user_id` mediumint(8) NOT NULL default '0',
  `user_active` tinyint(1) default '1',
  `username` varchar(25) NOT NULL default '',
  `user_password` varchar(32) NOT NULL default '',
  `user_session_time` int(11) NOT NULL default '0',
  `user_session_page` smallint(5) NOT NULL default '0',
  `user_lastvisit` int(11) NOT NULL default '0',
  `user_regdate` int(11) NOT NULL default '0',
  `user_level` tinyint(4) default '0',
  `user_posts` mediumint(8) unsigned NOT NULL default '0',
  `user_timezone` decimal(5,2) NOT NULL default '0.00',
  `user_style` tinyint(4) default NULL,
  `user_lang` varchar(255) default NULL,
  `user_dateformat` varchar(14) NOT NULL default 'd M Y H:i',
  `user_new_privmsg` smallint(5) unsigned NOT NULL default '0',
  `user_unread_privmsg` smallint(5) unsigned NOT NULL default '0',
  `user_last_privmsg` int(11) NOT NULL default '0',
  `user_emailtime` int(11) default NULL,
  `user_viewemail` tinyint(1) default NULL,
  `user_attachsig` tinyint(1) default NULL,
  `user_allowhtml` tinyint(1) default '1',
  `user_allowbbcode` tinyint(1) default '1',
  `user_allowsmile` tinyint(1) default '1',
  `user_allowavatar` tinyint(1) NOT NULL default '1',
  `user_allow_pm` tinyint(1) NOT NULL default '1',
  `user_allow_viewonline` tinyint(1) NOT NULL default '1',
  `user_notify` tinyint(1) NOT NULL default '1',
  `user_notify_pm` tinyint(1) NOT NULL default '0',
  `user_popup_pm` tinyint(1) NOT NULL default '0',
  `user_rank` int(11) default '0',
  `user_avatar` varchar(100) default NULL,
  `user_avatar_type` tinyint(4) NOT NULL default '0',
  `user_email` varchar(255) default NULL,
  `user_icq` varchar(15) default NULL,
  `user_website` varchar(100) default NULL,
  `user_from` varchar(100) default NULL,
  `user_sig` text,
  `user_sig_bbcode_uid` varchar(10) default NULL,
  `user_aim` varchar(255) default NULL,
  `user_yim` varchar(255) default NULL,
  `user_msnm` varchar(255) default NULL,
  `user_occ` varchar(100) default NULL,
  `user_interests` varchar(255) default NULL,
  `user_actkey` varchar(32) default NULL,
  `user_newpasswd` varchar(32) default NULL,
  `first_name` varchar(40) NOT NULL default '',
  `last_name` varchar(40) NOT NULL default '',
  `level` int(10) unsigned NOT NULL default '0',
  `disabled` tinyint(1) NOT NULL default '0',
  PRIMARY KEY  (`user_id`),
  KEY `user_session_time` (`user_session_time`)
) TYPE=MyISAM;