Hi Jan,
What version of Joomla / SEBLOD are you using? In actuality it is not an error but a notice. Are you experiencing something that is not working? You see this message when you have the Joomla debug option turned on:
Global Configuation>System>Debug System: Yes
You will also see the queries if you have the SEBLOD debug option turned on:
Global Configuration>SEBLOD>Site>Debug
So if you turn off the Debug options, the messages will should go away.
regards
Randy