[TYPO3] mysql_fetch error

[Michel]

Since this weekend I get the following error on my page?

Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result 
resource in /home/rds/public_html/t3lib/class.t3lib_db.php on line 741

Warning: Cannot modify header information - headers already sent by (output 
started at /home/rds/public_html/t3lib/class.t3lib_db.php:741) in 
/home/rds/public_html/tslib/class.tslib_fe.php on line 2614

I've updated static info tables to version 1.8 ? But I don't think that's 
the problem or is it?

I hope someone can give me a hint in the good direction.

Thanks in advance,

Michel