Forgot one thing, the error is happening only when following code is present:

$(document).ajaxSend(function(event, request, settings) {
 if (typeof(AUTH_TOKEN) == "undefined") return;
   settings.data = settings.data || "";
   settings.data += (settings.data ? "&" : "") + "authenticity_token=" + encodeURIComponent(AUTH_TOKEN);
});

Replying to [ticket:3155 jzajpt]:

When using Internet Explorer 6 & 7, simple code below uses POST method instead of GET (and for example in Rails causes invocation of wrong action when being RESTful):

> $.get("example", function(data){
>   alert(data);
> });
> 

Also, following examples use POST too instead of GET.

> $.ajax({
>   url: "example",
>   type: "GET",
>   success: function(html){
>    alert(html);
>   }
> });
> 

> $("#example").load("example");
> 

If the request includes *any* data, IE will assume POST. The $.ajax() code takes care of this for GET requests by appending settings.data to settings.url and clearing settings.data, but the global ajax events are triggered after that fix has been applied. So, on a GET request you must add to settings.url, not settings.data.