I received the same message when I initially installed Actuate, it turned out that I did not have the correct Oracle client installed on my p.c.. If your DB is Oracle 8.0, then you need Oracle Client 8.X, if the DB you are going against is Oracle 9.X, you will need that version installed on the client side as well. I had Oracle 7.2 installed on my client, but was attempting to hit a 9.2 DB. After upgrading, everything was o.k. Hope this helps.