Strange Problem: Templated checkbox column

Hi,

I've coded a templated column that will add a column of asp:Checkboxes
including an asp:checkbox on the column header, to a gridview. The checkbox
on the column header has Auto-postingback enabled and I've added an event
hanlder to handle the CheckChanged event. I've put some code to the
CheckChanged event hanlder. The templated column column is very simple
doesnt do anything other than mentioned above.

If I add this templated column on fly to a gridview which is also built
dynamically, then CheckChanged event handlder fires when I tick/untick the
column header checkbox, so no problem.

But if I add this templated column on fly to a gridview added to the page in
the designmode, then CheckChanged event handler fires only when I tick the
checkbox on the column header. Event hanlder is not called when I untick the
checkbox.

Anybody know reason to this behavior? How to change this behavior?

Dev