Could you please let me know whether the error appear if the ajax is disabled on the page and also if regular asp UpdatePanel is used instead of RadAjax?
Please find attached a sample application which demonstrates how you can ajaxify buttons of ModalPopupExtender.

Hi Maria,

Using a regular asp UpdatePanel with the ModalPopupExtender still generates the same error:

System.ArgumentException: Invalid JSON primitive: . at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializePrimitiveObject() at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth) at System.Web.Script.Serialization.JavaScriptObjectDeserializer.BasicDeserialize(String input, Int32 depthLimit, JavaScriptSerializer serializer) at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize(JavaScriptSerializer serializer, String input, Type type, Int32 depthLimit) at System.Web.Script.Serialization.JavaScriptSerializer.DeserializeObject(String input) at Telerik.Web.UI.RadWebControl.LoadPostData(String postDataKey, NameValueCollection postCollection) at Telerik.Web.UI.RadInputControl.LoadPostData(String postDataKey, NameValueCollection postCollection) at Telerik.Web.UI.RadWebControl.System.Web.UI.IPostBackDataHandler.LoadPostData(String postDataKey, NameValueCollection postCollection) at System.Web.UI.Page.ProcessPostData(NameValueCollection postData, Boolean fBeforeLoad) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)   

In regards to the errors I’m receiving in your example project; I receive the following error when clicking ‘lbEditDocInfo’:

Microsoft JScript runtime error: Sys.InvalidOperationException: Handler was not added through the Sys.UI.DomEvent.addHandler method.

The error occurs in:

var $removeHandler = Sys.UI.DomEvent.removeHandler = function Sys$UI$DomEvent$removeHandler(element, eventName, handler) {

    /// <summary locid="M:J#Sys.UI.DomEvent.removeHandler" />

    /// <param name="element"></param>

    /// <param name="eventName" type="String"></param>

    /// <param name="handler" type="Function"></param>

    var e = Function._validateParams(arguments, [

        {name: "element"},

        {name: "eventName", type: String},

        {name: "handler", type: Function}

    ]);

    if (e) throw e;

    Sys.UI.DomEvent._ensureDomNode(element);

    var browserHandler = null;

    if ((typeof(element._events) !== 'object') || (element._events == null)) throw Error.invalidOperation(Sys.Res.eventHandlerInvalid);

    var cache = element._events[eventName];

    if (!(cache instanceof Array)) throw Error.invalidOperation(Sys.Res.eventHandlerInvalid);

    for (var i = 0, l = cache.length; i < l; i++) {

        if (cache[i].handler === handler) {

            browserHandler = cache[i].browserHandler;

            break;

        }

    }

    if (typeof(browserHandler) !== 'function') throw Error.invalidOperation(Sys.Res.eventHandlerInvalid);

    if (element.removeEventListener) {

        element.removeEventListener(eventName, browserHandler, false);

    }

    else if (element.detachEvent) {

        element.detachEvent('on' + eventName, browserHandler);

    }

    cache.splice(i, 1);

}

Best regards,

Magnus