[Koha] Acquisitions and 'Biblios in koha'

Why is it when I hit 'Go' in .../acqui.simple/addbooks.pl (after typing in an ISBN) I never get any biblios listed in the "Biblios in koha" table, even though the biblio with that ISBN is in the bibioitems table. However it works fine when I type in the title. Looks like a bug to me. Am I missing something? I'm running Koha2.0.0. PS. My Koha.biblio table does not contain ISBN column. Tomasz Kotula