I got this error
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.
I got this error because I was using a ready made html5 template. The problem was duplicate form tag used multiple times in the template. Removing that get rid of the error.
To be exact my duplicate form tag was in the master page which was a bit hard to find.