[Koha] Problems with rebuild_zebra.pl -z

Hi, in my Koha 3.00.3 (a new Debian-Lenny testing installation), everytime I modify or delete a record, the zebraqueue table registers the changes with the "done" field=1. The update of Zebra will be unuseful, since rebuild_zebra.pl -z can't select records. Is there something wrong in my Zebra config? Or this is a bug? Thanks. Stefano