MySQL Database Errors - Possible Hack Attempts?

[King Justice]

Hello.

I received many database error emails today @ 3:15pm. I believe it was a hacking/injection attempt? Please help me troubleshoot the problem as I come today on 7:06pm, forum is working fine..but database errors via email.

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' (11)
/includes/class_core.php on line 311

MySQL Error :
Error Number :
Request Date : Wednesday, June 11th 2008 @ 12:15:23 AM
Error Date : Wednesday, June 11th 2008 @ 12:15:23 AM
Script : forumdisplay.php?f=13
Referrer :
IP Address : 75.178.78.86
Username :
Classname : vB_Database
MySQL Version :