MySQL Connect Error
 

Hi, i get a strange error in my email...the forum is working ok though

Code:
Database error in vBulletin :

mysql_connect() [function.mysql-connect]: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
/var/www/vhosts/site.com/httpdocs/includes/class_core.php on line 311
what could be the problem?
10x