Mysterious database error

[av8or1]

Hi-

I am running vB 4.1.3 and have been for a year now. I have never encountered any type of database error, but recently I received - via email - the following:

Database error in vBulletin 4.1.3:

Invalid SQL:

SELECT socialgroupcategory.title
FROM socialgroupcategory AS socialgroupcategory
WHERE socialgroupcategory.socialgroupcategoryid IN (-99) union select username from user where userid=6 and row(1,1)>(select count(*),concat( (select user.username) ,0x3a,floor(rand(0)*2)) x from (select 1 union select 2 union select 3)a group by x limit 1) -- /*);

MySQL Error : Duplicate entry 'lehlom:1' for key 'group_key'
Error Number : 1062
Request Date : Saturday, April 14th 2012 @ 01:17:57 PM
Error Date : Saturday, April 14th 2012 @ 01:17:57 PM
Script : http://www.russiancarclub.com/forum/...php?do=process
Referrer :
IP Address : 212.75.216.254
Username : Unregistered
Classname : vB_Database_MySQLi
MySQL Version :

Anyone ever seen this before? BTW, I read the recent article regarding a separate database error and ran the suspect files diagnostic per Lynn's recommendation. However I didn't see anything suspicious, just files that are a part of my add-ons. And that list consists of:

Article Forum
Attachment Gallery
Auto Database Backup
Change Posts Owner
Cinvin
GlowHost
LAM
MARCO1
Members who have visited
Picture and Album Gallery
Reply to All - PM
Skimlinks
Spiders Display
VB Pro Garage
vBa

Thanks!

Jerry