objAdapter.TableMappings.Add("Table1", "tblUsers")Thank you for the input Keith. I wasn't using default table names when creating them in the DataSet so unfortunatly table mappings didn't help. But after buring myself in the code some more I did find out what my problem was. When I was calling the Update command, I was supplying the Dataset (Object) and the Table name (String) as the parameters. For some reason the Update command was not liking this usage, even though it is one of the proper signatures. I changed the parameters to be just a reference to the Table object itself inside the DataSet, and then it worked fine.