A few things to check. First, are you using the Merrant ODBC drivers installed by the Oracle Client software? Second, did you correctly define and test the ODBC datasource defined on the computer where IIS is running? Third, when you test the connection do you see entries appended to the end of listener.log - if not then you're not getting that far and can isolate the problem back to the client setup. The error message I think is a catch-all, and probably has a hundred causes.