Database error in vBulletin - Can't connect to local MySQL server through socket

Database error in vBulletin :

mysql_connect() [<a href='function.mysql-connect'>function.mysql-connect</a>]: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (11)/home/braces/public_html/forums/includes/class_core.php on line 311

MySQL Error : Error Number : Request Date : Sunday, December 20th 2009 @ 11:58:59 AMError Date : Sunday, December 20th 2009 @ 11:58:59 AMScript : http://localhost/forums/misc.php?do=linkbacksReferrer : IP Address : 212.95.58.93Username : Classname : vB_DatabaseMySQL Version :