[Typo3] Warning: mysql_fetch_row()????

[Miguel Angel Calleja Lázaro]

When I click in list and I selected a Pid, on the top appears me this 
error:*

Warning*: mysql_fetch_row(): supplied argument is not a valid MySQL 
result resource in */var/lib/typo3/typo3_3.8/t3lib/class.t3lib_db.php* 
on line *754*

*Warning*: Cannot modify header information - headers already sent by 
(output started at 
/var/lib/typo3/typo3_3.8/t3lib/class.t3lib_db.php:754) in 
*/var/lib/typo3/typo3_3.8/typo3/template.php* on line *601

*Whats means? and how can i solve it? thanks