Wie kann das sein, dass es mal funktioniert mal nicht -> MySQL Fehler in PHP Script

Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') ORDER BY thread.time DESC LIMIT 5' at line 4' in /var/www/web249/html/wp-content/plugins/wordpress-wbb_bridge/WcfWbbLatestPosts.class.php:181 Stack trace: #0 /var/www/web249/html/wp-content/plugins/wordpress-wbb_bridge/WcfWbbLatestPosts.class.php(181): PDOStatement->execute(Array) #1 /var/www/web249/html/wp-content/plugins/wordpress-wbb_bridge/widget.php(44): WcfWbbLatestPosts->displayThreads(Array, 5) #2 /var/www/web249/html/wp-includes/widgets.php(217): WBB_Posts_Widget->widget(Array, Array) #3 [internal function]: WP_Widget->display_callback(Array, Array) #4 /var/www/web249/html/wp-includes/widgets.php(1082): call_user_func_array(Array, Array) #5 /var/www/web249/html/wp-content/themes/ouya_leetpress_new/sidebar.php(4): dynamic_sidebar() #6 /var/www/web249/html in /var/www/web249/html/wp-content/plugins/wordpress-wbb_bridge/WcfWbbLatestPosts.class.php on line 181

$sql = "SELECT thread.lastPostID, thread.lastPoster, thread.lastPosterID, thread.topic, thread.lastPostTime, thread.threadID, board.title, thread.views, thread.replies, thread.userID, thread.username
				FROM wbb".WCF_N."_thread thread
				LEFT JOIN wbb".WCF_N."_board board ON (thread.boardID = board.boardID)
				WHERE thread.boardID IN (".implode(',',$boardIDs).")
				ORDER BY thread.time DESC
				LIMIT ".intval($limit);

"SELECT board.parentID, board.boardID, acl_group_everybody.optionValue as visibileToEverybody, acl_group_guest.optionValue as visibileToGuest
				FROM wbb".WCF_N."_board board
				LEFT JOIN wcf".WCF_N."_acl_option_to_group acl_group_everybody ON (acl_group_everybody.optionID = ".$aclOptionID." AND acl_group_everybody.objectID = board.boardID AND acl_group_everybody.groupID = 1)
				LEFT JOIN wcf".WCF_N."_acl_option_to_group acl_group_guest ON (acl_group_guest.optionID = ".$aclOptionID." AND acl_group_everybody.objectID = board.boardID  AND acl_group_guest.groupID = 2)";

 parentID 	boardID 	visibileToEverybody 	visibileToGuest 	
NULL	11 	1 	1
NULL	11 	1 	1
NULL	11 	1 	1
NULL	11 	1 	0
NULL	18 	1 	1
NULL	18 	1 	1
NULL	18 	1 	1
NULL	18 	1 	0
NULL	28 	1 	1
NULL	28 	1 	1
NULL	28 	1 	1
NULL	28 	1 	0
NULL	35 	0 	1
NULL	35 	0 	1
NULL	35 	0 	1
NULL	35 	0 	0
11 	12 	NULL	NULL
11 	13 	NULL	NULL
11 	14 	NULL	NULL
11 	15 	NULL	NULL
11 	16 	NULL	NULL
11 	17 	NULL	NULL
11 	34 	NULL	NULL
11 	45 	NULL	NULL
11 	46 	NULL	NULL

$this->boardList = array();
		$this->boardChilds = array();
		
		// list every board child
		foreach ($result as $board) {
			$this->boardList[$board['boardID']] = $board;
			if ($board['parentID']) {
				if (empty($boardChilds[$board['parentID']])) $boardChilds[$board['parentID']] = array();
				$this->boardChilds[$board['parentID']][] = $board['boardID'];
			}
		}
		
		$finalBoardList = array();
		foreach ($this->boardList as $boardID => $board) {
			if ($this->isVisible($board)) $finalBoardList[] = $boardID;
		}
		return $finalBoardList;

$finalBoardList = array();
        foreach ($this->boardList as $boardID => $board) {
            if ($this->isVisible($board)) $finalBoardList[] = $boardID;
        }

	private function isVisible ($board) {
		$visible = $this->isVisibleHelper($board);

		if ($visible === null) {
			while ($visible === null) {
				if ($board['parentID'] === null) {
					$visible = true;
				}
				else {
					$board = $this->boardList[$board['parentID']];
					$visible = $this->isVisibleHelper($board);
				}
			}
		}
		return $visible;