Form.Show and events

Here is more info if anyone can throw light on this I'd be most
grateful:
in my old VS 2005 version, as soon as I set the combo box SelectedValue,
the SelectedItemChanged event is fired.

In my new version in VS 2008 calling SelectedValue does not immediately
raise the event - the event is raised later when I call Show().

I have no clue why this can be happening.

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