Need urgent help- registration problems

[h@ck3r]

I have some new members trying to register on my sire (Quite a few), but they are not receiving their confirmation emails.

I am getting these emails to my inbox with the error log:

Database error in vBulletin :

mysql_connect() [<a href='function.mysql-connect'>function.mysql-connect</a>]: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) /home2/kjgut/public_html/MYWEBSITE.co.uk/forum/includes/class_core.php on line 311

MySQL Error :
Error Number :
Request Date : Tuesday, February 24th 2009 @ 03:08:03 PM
Error Date : Tuesday, February 24th 2009 @ 03:08:03 PM
Script : hXXp://www.MYWEBSITE.co.uk/forum/ajax.php?do=shownewnotifications
Referrer : hXXp://www.MYWEBSITE.co.uk/forum/FORUM-NAME/1187-THREAD-TITLE-post11523.html
IP Address : 80.5.76.230
Username :
Classname : vB_Database
MySQL Version :

Can someone please help me finding the problem?

Thanks