Quick resolution: Give full permission to AUTHENTICATED USERS in following folders. a) ORACLE_HOME b) Program Files\ORACLE Check your PATH. You might have installed different clients in your system and your .NET application is pointing to a home with inappoperiate client. What your .NET application should load is OCI.DLL with File version more than 8.1.7. According to the MSDN document Oracle and ADO.NET: "The .NET Framework Data Provider for Oracle provides access to an Oracle database using the...