It means that you are using an older version of the blast software but that you already have the newest DB at hand.
the newest blast version work with a new blastDB type (=version 5 ), the older still work with v4 . What you download currently from ncbi is the version 5 DBs (the version 4 is only available in a kind of legacy mode)
solution: get the newest blast software version (or revert the DB to an older version) , Personally I would go for updating the software