Why ASP.NET CheckedChanged not fired?

I've a HTML Table with CheckBox in each cell. My first row below my Header cell have a problem, when I check it, the Event is correctly fired but when I uncheck it, there are no event. The other cell and Checkbox work correctly (Check/Uncheck with event). When I did not create the Header Cells work correctly.

See my cells don't work uncheked event:

My Code Behind :

http://ift.tt/1SYeFI8

(The syntax of variables is imposed on me)