在分类主题的时候很多sql错误，请问可能是什么问题？

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /usr/local/www/htdocs/pc/default.php on line 308

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /usr/local/www/htdocs/pc/default.php on line 308

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /usr/local/www/htdocs/pc/default.php on line 308

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /usr/local/www/htdocs/pc/default.php on line 308
--
FROM 222.28.219.222