The Textbox component will not fire an onChange event when:
1. There is already text in the Textbox
2. Some text is selected with the mouse
3. The mouse button release happens outside of the Textbox's area.

I can actually make this happen with several other scenarios as well.
It seems that the Textbox onChange event is actually triggered by a
mouse button release (MOUSE_UP) within the Textbox's screen area. I
can change textbox content at will and avoid firing this event. This
will be a problem in my application where I am trying to detect changes
and enable a 'Save' button.