Database error?

[adam_99uk]

I got emailed the following error; what does it mean? I have never been emailed an error before and have no idea how to fix it or what is wrong either.

Database error in vBulletin :

Link-ID == false, connect failed
mysql error:

mysql error number: 0

forum/private.php?do=newpm&userid=440

Thats part of the path of the script with the problem on the email.

[Mark.B]

Your MySQL server is down - contact your hosts about this.

[Boxy]

This error could be caused by any of the following:
1) The database information in your config.php file is wrong (in which case your forums won't work at all.)
2) The user doesn't have permission to access the database specified in config.php.
3) The database doesn't exist.
4) MySQL isn't accepting new connections. (The server could either be down or has reached it's maximum connections limit.)

Almost all the problems that cause the Link-ID == false error are beyond our power to resolve, and must be dealt with by your host.