A bit late now but I just had the same problem so heres what sorted it for me.
Look at the below and search for primary key: http://msdn.microsoft.com/en-us/library/system.data.common.dbcommandbuilder.aspx "The SelectCommand must also return at least one primary key or unique column. If none exist, an InvalidOperationException exception is generated, and the commands are not generated. " "To generate INSERT, UPDATE, or DELETE statements, the DbCommandBuilder uses the SelectCommand property to retrieve a required set of metadata automatically" So you need to have a primary key on your table. That sorted it for me.
