Hello everyone,

I've created a Address book page (By following the asp.net 4 website using C#). Originally it was working fine, I could edit, delete and add new data. Now how ever I am getting an error when ever I try to click on edit or anything else and I am pretty sure that I have not changed anything at all. So I am somewhat confused as to what has happened. what can I do to overcome this and why did this happen?:

PHP Code:
JavaScript runtime errorSys.WebForms.PageRequestManagerServerErrorExceptionInvalid postback or callback argument
Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page.  
security purposesthis feature verifies that arguments to postback or callback events originate from the server control that originally rendered them.  
the data is valid and expected
the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation

Also a random file opens up and a throw error is highlighted as the message appears:

PHP Code:
        var eventArgs = new Sys.WebForms.EndRequestEventArgs(errordata data.dataItems : {}, executor);
        if (
error && !eventArgs.get_errorHandled()) {