ADOQuery til DBGrid

Har en TADOQuery jeg gerne vil have vist i et DBGrid.
Får fejl EAccessViolation i linien: DBGrid1.DataSource.DataSet := query;

Hva' der galt ? Eller skal det gøres på en anden måde ?

procedure TfrmDBGrid.InitControls(JupPath:string);
var
  ADOConnection : TADOConnection;
  query        : TADOQuery;
begin
  ADOConnection := TADOConnection.Create(nil);
  query        := TADOQuery.Create(nil);
  try
    with ADOConnection do begin
      LoginPrompt := False;
      Close; 
        ConnectionString := 'Provider=Microsoft.Jet.OLEDB.4.0;Data Source='+JupPath+';Persist Security Info=False';
    end;

    query.Connection := ADOConnection;
    query.SQL.Clear;
    query.SQL.Add('SELECT BOREHOLENO, DRILLDEPTH, ELEVATION, XUTM, YUTM');
    query.SQL.Add('FROM BOREHOLE');
    query.ExecSQL;
    query.Open;

    ShowMessage(IntToStr(query.RecordCount));

    DBGrid1.DataSource.DataSet := query;
  finally
    with ADOConnection do begin
      Close;
      Free;
    end;
    query.Free;
  end;
end;