IE windows blocked by modal dialogue can get focus when user selects the IE process in task bar.

Note :
  Although the focus moves to the IE windows, user can not affect any action to the window.
  The IE window has buttons, but no action occurs by clicking any button.
  Just focus moves to the IE window.

What is problem :
  When focus moves to the IE window, the IE window goes up foreground.
  That causes to hide the dialogue which is waiting for user operation.
  Because user can not see the situation that the dialogue is waiting, 
  user minsunderstand freeze occurs.

REPRODUCE:
  1) Open the attached html 
  2) Set some value ( 300 ?) to text field
  3) Click "New Window" and then click "Call dialogue" as quick as possible
    Dialogue appears at the top of windows layer.
    You can see 2 IE items in IE task bar
  4) Select the IE process created at step 3) in task bar

  Focus moves to the IE window and dialogue disappears (goes to background)