I was having similar problems. My story is a bit unique.
Gameservers.com is hosting my 3 TF2 servers.
3ix.com for MySQL database, and web portal for Sourcebans
Went with 3ix only because they are on the whitelist shared for these forums and they have a good price.
Running latest version of Sourcebans 1.4.10
at start, I had some issues with the gameservers connecting to the MySQL database but 3ix support helped.
Worked great for 1 week until my 3ix server crashed for like 30 minutes, now sourcebans(game server side) cannot seem to communicate with the MySQL database anymore.
Through many support posts with 3ix:
We are at this error when I test ban my alt acount in the game server:
L 11/18/2012 - 11:46:48: [sourcebans.smx] Verify Insert Query Failed: Subquery returns more than 1 row
the ban works temporarily for the server.
the ban is not global for all 3
the ban does NOT list on the SB portal page: http://www.databaseboy.com/bans/index.php
Any help is appreciated!