Ok i've changed to debug. restarted ispconfig enabled autoresponder but i don't have anything new in ispconfig logs:
18.10.2011-12:20 - DEBUG - There is already an instance of server.php running. Exiting.
and in cron.log still the same message:
Use of uninitialized value $_ in join or string at /usr/share/perl5/Debconf/DbDriver/Stack.pm line 111.