Bonk troubleshooting help

Hey guys. My vanilla forum has been running fine for ages and I just woke up to find it down with a bonk error. Here is the error message. Anybody know how I can fix this?

Fatal Error in Gdn_Database.Connection();

An error occurred while attempting to connect to the database
SQLSTATE[HY000] [2054] The server requested authentication method unknown to the client
The error occurred on or near: /home/vtcgvqbi/public_html/library/database/class.database.php
57:             $this->_Connection = new PDO(strtolower($this->Engine) . ':' . $this->Dsn, $this->User, $this->Password, $this->ConnectionOptions);
58:             if($this->ConnectionOptions[1002])
59:                $this->Query($this->ConnectionOptions[1002]);
60:          } catch (Exception $ex) {
61:             trigger_error(ErrorMessage('An error occurred while attempting to connect to the database', $this->ClassName, 'Connection', $ex->getMessage()), E_USER_ERROR);
62:          }
63:       }
64:       
65:       return $this->_Connection;
Backtrace:
/home/vtcgvqbi/public_html/library/database/class.database.phpPHP::Gdn_ErrorHandler();
[/home/vtcgvqbi/public_html/library/database/class.database.php:61] PHP::trigger_error();
[/home/vtcgvqbi/public_html/library/database/class.database.php:275] Gdn_Database->Connection();
[/home/vtcgvqbi/public_html/library/database/class.sqldriver.php:1657] Gdn_Database->Query();
[/home/vtcgvqbi/public_html/library/database/class.sqldriver.php:941] Gdn_SQLDriver->Query();
[/home/vtcgvqbi/public_html/library/core/class.model.php:383] Gdn_SQLDriver->GetWhere();
[/home/vtcgvqbi/public_html/library/core/class.model.php:366] Gdn_Model->GetWhere();
[/home/vtcgvqbi/public_html/applications/dashboard/models/class.usermodel.php:472] Gdn_Model->GetID();
[/home/vtcgvqbi/public_html/applications/dashboard/models/class.usermodel.php:643] UserModel->GetID();
[/home/vtcgvqbi/public_html/library/core/class.session.php:280] UserModel->GetSession();
[/home/vtcgvqbi/public_html/library/core/class.auth.php:36] Gdn_Session->Start();
[/home/vtcgvqbi/public_html/bootstrap.php:168] Gdn_Auth->StartAuthenticator();
[/home/vtcgvqbi/public_html/index.php:41] PHP::require_once();
Variables in local scope:
[php_errormsg] 'PDO::__construct(): The server requested authentication method unknown to the client [mysql_old_password]'
[ex] array (
  'errorInfo' => NULL,
)