access violation when setting forms WindowState property

Okay, here's the situation.  I have a form that displays some data about
university alumni in a grid.  I want the user to be able to double-click
a row in the grid and have minimize the form and display the
application's main form with data about the selected alumnus.  When the
user later selects the option to display the grid, I want that form that
contains the grid to be maximized (and effectively hide the
application's main form).

My problem is that whenever I attempt to set the grid form's
WindowState, I get an access violation.  This occurs whether I set the
form's WindowState in the grid double-click event or in the main form
procedure that returns to the form containing the grid.

Here are the code snippets.  The grid's double click event is first and
the procedure in the main form is next.  In both cases, the access
violation occurs when I set the WindowState property.

procedure TQueryResultsForm.ResultsExtGridDblClick(Sender: TObject);
var strUncID: string;
begin
  strUncID := TrimHyphens(ResultsExtGrid.Cells[0, ResultsExtGrid.Row]);
  MainForm.IDNumInEdit.Text := strUncID;
  QueryResultsForm.WindowState := wsMinimized;
end;

procedure TMainForm.QueryEngineMenuItemClick(Sender: TObject);
var QueryWizardTypeForm: TQueryWizardTypeForm;
    i: integer;
    bolFormFound: boolean;
begin
  try
    Screen.Cursor := crHourGlass;
    PageControl1.ActivePage := GeneralTab;
    CloseDataSets;
    bolFormFound := false;
    for i := 0 to Application.ComponentCount - 1 do
      if Application.Components[i].Name = 'QueryResultsForm' then
        begin
          bolFormFound := true;
          QueryResultsForm.WindowState := wsNormal;
          break;
        end;
    if not bolFormFound then
      begin
        QueryWizardTypeForm := TQueryWizardTypeForm.Create(Application);
        QueryWizardTypeForm.Show;
      end;        
  finally
    Screen.Cursor := crDefault;
  end;
end;

--
================================================
Ray Porter
Applications Analyst Programmer
Administrative Information Services, UNC-CH
Phone: 966-5878
email: ray_por...@unc.edu
       dra...@email.unc.edu
Home Page: http://www.unc.edu/~dragon/

"Meddle not in the affairs of dragons,
for you are crunchy and taste good with ketchup."