get exceptions while using LoadViewState in ascx

hi,
Im trying to use below code in three.ascx which is pasted on two.ascx page
and two.ascx is pasted on one.aspx page. But "LoadViewSt ate" gives
exceptions mentioned below
protected override object SaveViewState()
{ object[] SaveState;
SaveState = new object[1];
SaveState[0] = this.chkItem.Ch ecked;
return SaveState;
}
protected override void LoadViewState(o bject obj)
{ object[] LoadState;
LoadState = (object[])obj;
if(LoadState != null)
{
this.chkItem.Ch ecked = (string)LoadSta te[0];
}
}
GET EXCEPTIONS: Failed to load viewstate. The control tree into which
viewstate is being loaded must match the control tree that was used to save
viewstate during the previous request. For example, when adding controls
dynamically, the controls added during a post-back must match the type and
position of the controls added during the initial request.

how can i come out from these exceptions
Cheers,
Sam