Sudden Database error: Access denied for user
 

Everything was running just fine, that my forum suddenly started giving me the following error. I wasn't making any changes to the forum dbase or the forum itself, so I really am at sea as to what has gone wrong in here. Now my inbox is virtually inundated with hundreds of emails - all describing the same error - such as the following but all showing different requests.

Can anyone help?


Code:
Database error in vBulletin :

mysql_connect() [function.mysql-connect]: Access denied for user 'username'@'localhost' (using password: YES)
/home/username/public_html/forum/includes/class_core.php on line 311

MySQL Error :
Error Number :
Request Date : Thursday, May 7th 2009 @ 06:20:25 AM
Error Date : Thursday, May 7th 2009 @ 06:20:25 AM
Script : http://wccftech.com/forum/showthread.php?t=22113&page=2
Referrer :
IP Address : 75.52.124.143
Username :
Classname : vB_Database
MySQL Version :