Invisible Checkboxes are automatically unchecked on three postbacks

Hi,
I have a very complex webform aspx page. I have two checkboxes which I have checked all the references of and nowhere in the project I found the code to set the Checked property to false. When they are visible on the first time page load, I check them with mouse clicks and submit them, in all subsequent postbacks they are Visible=false on serverside...
The problem is, on the 3rd postback, the Checked property is automatically set to false.
I have checked to see they are declared as protected members, I have searched for ' FindControl("checkboxid") ' occurances in whole project, there is javascript code manipulating it but if they are Visible=false on serverside, javascript cant see it, can somebody give me some idea what might be happening and what else should I check ?

Thanks
Fahad
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