Tony,
Which provider are you using to connect to the AS/400?
IBM Client Access, Microsoft's product, another's companies product? (by
product I mean the Ole DB or ODBC provider you are using and not
System.Data.OdbcConnection or System.Data.OleDbConnection!).
You would need to check the documentation of the product you are using.
If you are using IBM Client Access, you need to be on Client Access V5R2 to
be fully supported from .NET. The following links provide details, samples,
and connection strings.