vBulletin Database Error! - socket

[محروم.كوم]

I am spasmodically getting the following error:

Database error in vBulletin :

mysql_connect() [function.mysql-connect]: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (11) /home/XXXXXXXXXX/XXXXXX/forum/includes/class_core.php on line 311

MySQL Error :
Error Number :
Request Date : Monday* December 7th 2009 @ 12:25:44 PM
Error Date : Monday* December 7th 2009 @ 12:25:44 PM
Script : http://www.XXXXXX/index.php

Referrer :
IP Address : XXX.XXX.XXX.XXX
Username :
Classname : vB_Database
MySQL Version :

These are happening at any time and for durations of a minute or so where I get bombarded with error emails - they can even happen in the middle of the night when site use is at its lowest. The script page* the ip address and the (11) the error msg refers to is always different

The host has upped the max simultaneous connections to over 2*000 and together we have looked at many different causes with the host saying that it has to be a software issue.

Using the latest version of vb (not 4) and mysql 5+ __DEFINE_LIKE_SHARE__