Informix Connect 7.20 : BUG ???

I had problems using dynamic queries from Delphi applications. Here is my configuration : server = SCO OpenServer 5 with Informix SE 5 database and I-NET 5.03.UC1 . On the client side, I work with Windows 95, Delphi C/S 2.01 , SQL-Links 3.5 and Informix Connect 7.20. When I prepare a dynamic queries with a restriction on an indexed char column, it looks like it operates a sequential research, so the answer comes after 30 long seconds; whereas I have no problem with the same query without parameters. If I send the same query using DBaccess on the server, the answer is immediate. If the dynamic query has a restriction on an indexed integer column, the answer is immediate. I tried to replace Informix Connect 7.20 with SCO SQL-Retreiver 4.0 and I now have no more problems with my queries. So, I think that the problem comes from Informi Connect 7.20. Have you ever heard about that ? Beatrice. Association Hospitali're du Bassin de Longwy. France.