MSQL problem

[Devanand]

Hello,

I just open a email I used in vbulletin which I didn't open for a months and I saw that I am getting tons of email every day. All email are almost the same and look like this:

Database error in vBulletin :

mysqli_real_connect() [<a
href='function.mysqli-real-connect'>function.mysqli-real-connect</a>]: (42000/1203):
User ********** already has more than 'max_user_connections' active connections
.../public_html/includes/class_core.php on line 1138

MySQL Error   : 
Error Number  : 
Request Date  : Saturday, April 3rd 2010 @ 04:57:33 AM
Error Date    : Saturday, April 3rd 2010 @ 04:57:33 AM
Script        : http://mysite.com/register.php
Referrer      : http://mysite.com/register.php
IP Address    : 212.117.165.184
Username      : 
Classname     : ******_Database_MySQLi
MySQL Version :

Of course, "Script" and "Referrer" are different in every email but this few lines at the begining are same in each of them.
I found that file and line 1138 but that is all I know to do now.
I am on dedicated server i7 ( 8 cores ) / 12 GB RAM so it must me some solution.
What is problem and how to fix it?

Thank you