Plz help upgrade error
 

I am trying to upgrade vbulletin to 3.8.3 from 3.8.1
I am getting db error
Database error in vBulletin :
mysql_connect() [function.mysql-connect]: Access denied for user 'root'@'localhost' (using password: NO)
/home/mysite/public_html/forum/upload/includes/class_core.php on line 311