Pop Up msg through eConfigurator Script

Hi All,

There is a requriement to show the User Message As a PopUp to user while running the econfigurator script event.
The below has been tried: by giving the Raise Error Text on
1. Cfg_AttributeChanged or Cfg_ChildItemChanged event:- It shows the User Message as popup after which the Product Instance crashes.
2. Cfg_AttributeSelected or Cfg_ChildItemSelected events:-It shows in Conflict Message Format and after clicking on proceed button Instance works fine.

1)Why is the behaviour of Raise Error Text different on different events?( one event shows as popup, in other events shows as configurator conflict like message)