Error order list

Hello,

Today I discoverred an error at the bottom of the order list. Anyone an idea what this is and what to do?

Warning: mysql_real_escape_string(): 73 is not a valid MySQL-Link resource in /var/www/vhosts/mysite.nl/httpdocs/system/database/mysql.php on line 58

Warning: mysql_query(): 73 is not a valid MySQL-Link resource in /var/www/vhosts/mysite.nl/httpdocs/system/database/mysql.php on line 22

Warning: mysql_error(): 73 is not a valid MySQL-Link resource in /var/www/vhosts/mysite.nl/httpdocs/system/database/mysql.php on line 50

Warning: mysql_errno(): 73 is not a valid MySQL-Link resource in /var/www/vhosts/mysite.nl/httpdocs/system/database/mysql.php on line 50

Notice: Error:
Error No:
SELECT * FROM yl_setting WHERE store_id = '0' AND `group` = '' in /var/www/vhosts/mysite.nl/httpdocs/system/database/mysql.php on line 50

Thanks

Nobody who has an idea what this error means?