After working fine for a couple of years I NOW get the following error message appearing when I select the Upload button in Admin>File Manager: 

A critical error has occurred.
Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation="true"/> 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.
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Can someone please advise how I can fix this so we can upload files via Fiel Manager again.

Thanks
MikeT

Hi,

Got same error here last week after 3 years. I am using version dotnetnuke 3.XX with access database. After getting this error i added EnableEventValidation="false"  to my default.aspx page directive error get fixed but now FCKEditor is not working.

Any clue? Are these things that i am facing related to eachother?

Any help is very much appreciated.

Thanks.

Is this because of the well known ASP.NET encrypted v13wstat3 issue? (ie if you do a postback before the page finishes loading then it can die.)  So, does it make a difference if you wait for the page to load or not?

JK