> Invalid postback or callback argument. Event validation is enabled using in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.
I've prepared a test application. All you have to do is download the archive and run the project. On the web page select the 3 items, press Add all, then move the third element up one level and then hit "Button". The error will show up. Turning event validation off is by no means acceptable. Can anyone help me, I've spent two already days without finding a solution.
: http://cid-c9672af9b84b07ef.skydrive.live.com/self.aspx/TestApp/TestProject.zip FYI: I downloaded your app and never got this error - I did, however, get an error about col1 not being a part of the data table, or something like that (not looking at it right now). You might want to check to make sure your example causes this error, because it doesn't for me.