Javascript runtime error

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?:

JavaScript runtime error: Sys.WebForms.PageRequestManagerServerErrorException: 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.

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


        var eventArgs = new Sys.WebForms.EndRequestEventArgs(error, data ? data.dataItems : {}, executor);
        Sys.Observer.raiseEvent(this, "endRequest", eventArgs);
        if (error && !eventArgs.get_errorHandled()) {
          throw error;

can no one help? Should post the aspx and.CS pages? or the web.config file?