Treeview Postback
as per http://msdn2.microsoft.com/en-us/library/system.web.ui.webcontrols.treeview.treenodecheckchanged.aspx
TreeView.TreeNodeCheckChanged occurs when some other control does the postback,
but "changing a check box does not cause a post back"
Brian Goldfarb's Blog: http://blogs.msdn.com/bgold/archive/2006/09/08/746510.aspx
google search "asp.net 2.0 treeview postback"
interesting result: http://steveorr.net/articles/Ajax.aspx