Hi Andy
I added the following code to a blank form with a TImageEnView and it worked without error:
procedure Tfmain.Button1Click(Sender: TObject);
const
  w = 500;
  h = 500;
var
  ie: TImageEnView;
begin
  ie := ImageEnView1;
  ie.IEBitmap.Allocate(w, h, ie24RGB);
  // Draw Rectangle
  with ie.IEBitmap.IECanvas do
  begin
    Pen.Width:= 5;
    Pen.Style:= psSolid;
    Pen.Mode:= pmCopy;
    Pen.Color:= clGreen;
    Brush.Style:= bsClear;
    Rectangle(1, 1, w-1, h-1);
  end;
  // Refresh view
  ie.Update();
What version of Delphi are you using? Is ie.LegacyBitmap set to false?
Nigel 
Xequte Software
www.imageen.com