You can reproduce this bug by your own, try this:

DataSet DataSet1 = new DataSet();
DataTable customers = new DataTable("Customers");
customers.Columns.Add("CustID");
DataSet1.Tables.Add(customers);

DataTable orders = new DataTable("Orders");
orders.Columns.Add("CustID");
orders.Columns.Add("test");
DataSet1.Tables.Add(orders);

// Get the DataColumn objects from two DataTable objects
// in a DataSet. Code to get the DataSet not shown here.
DataColumn parentColumn =
   DataSet1.Tables["Customers"].Columns["CustID"];
DataColumn childColumn =
   DataSet1.Tables["Orders"].Columns["CustID"];
// Create DataRelation.
DataRelation relCustOrder;
relCustOrder = new DataRelation("CustomersOrders", parentColumn,
childColumn, true);
// Add the relation to the DataSet.
DataSet1.Relations.Add(relCustOrder);

DataSet1.Tables["Customers"].ChildRelations[0].ChildColumns[0] =
DataSet1.Tables["Orders"].Columns["test"];

If you try this under .NET 1.0
DataSet1.Tables["Customers"].ChildRelations[0].ChildColumns[0] = "CustID"

In .NET 2.0 DataSet1.Tables["Customers"].ChildRelations[0].ChildColumns[0] =
"test"

Thanks

Marco