Site down - user database error

[BonsaiNut]

Went off on vacation and wouldn't you know, my site crashed while I was away. Problem with my user DB - I keep getting spammed with errors any time someone tries to login to the site. I cannot log into the site myself, and cannot access the AdminCP. Here is the error I get when I try to login to the AdminCP:

Database error in vBulletin 3.6.2:

Invalid SQL:
INSERT INTO cpsession (userid, hash, dateline) VALUES (X, 'XXXXXXXXX', XXXXXXXXX);

MySQL Error : Access denied for user: 'XXXXX' to database 'XXXXX'
Error Number : 1044
Date : Wednesday, September 5th 2007 @ 03:58:25 AM
Script : http://www.bonsainut.com/forums/login.php?do=login
Referrer : http://www.bonsainut.com/forums/admincp/
IP Address : 68.109.72.127
Username : BonsaiNut
Classname : vb_database

Any help?

Why would this suddenly occur when I have been running the site successfully for 9 months now, and I am the only one with ADMIN permissions and I was out of town?