Joomla + Mootools XMLHttpRequest problem.

Question

I'm building a Joomla extension and i'm trying to send some data to a php script, with MooTools, to be saved in a database.

This is the code for the request :

    myReq: new Request({
        url: '/index.php?option=com_calculator&task=saveData',
        method: 'post',
        onSuccess: function (responseText, responseXML) {
            console.log(reponseText);
        }
    })

When i run it Firebug throws this error:

Permission denied for <http://localhost&gt; to get property XMLHttpRequest.channel

I've read around and think it could be related to the same domain policy for Ajax,but i couldn't get a fix on it.