My first guess would be that you have changed/add indexing on the o attribute without re-indexing. slapd looks in the index, finds no matching attribute in the index, and there's no point in it looking further (or the index is useless).
Update the indexes by running 'slapdindex' while slapd isn't running, and it should work (or, you have another problem).
--Quanah
-- Quanah Gibson-Mount Principal Software Developer ITS/Shared Application Services Stanford University GnuPG Public Key: http://www.stanford.edu/~quanah/pgp.html