MVC :: How To Handle UnauthorizedRequest By Ajax Post

I handle unauthorized request with custom code. Problem is that after calling HandleUnauthorizedRequest method, Application_Error is called with Server.GetLastError() exception "Server cannot set content type after HTTP headers have been sent." .

I debug for a while and no clue. Here is my code.

When I debug the call stack is:

AuthorizeCore() -> HandleUnauthorizedRequest() -> Application_Error() -> javascript error in MicrosoftAjax.js

[Code]....

-- javascript code

function RemoveQuoteFromThemePageComplete(content) {
var JsonActionResult = content.get_response().get_object();
if (JsonActionResult.ContentType == "javascript") {
eval(JsonActionResult.Data);
}
if (JsonActionResult.Success) {
$.fx.off = false;
var sayingID = JsonActionResult.Data;
$("#saying-id-" + sayingID).fadeOut("slow", function () {
$(this).parent().remove();
});
}
}