I am focusing on an element for Joomla 1.7, and Joomla 1.7 works together with Mootools 1.3. Before that, the right means by mootools was Ajax class. However in Mootools, when i read, I have to use Request class.

Ok, after i use the Request class and have a look with Google Inspector debuging step-by-step the Request definition and ask for send() call. I can tell that, it executives the send however it does nothing (ignores onSuccess, ignores OnException, etc).

And when I look on chrome javascript console there is nothing.

function addValue(value) {
    var id = $('selectedval').getProperty('value');
    var url = 'index.php?option=com_kaltura&controller=fieldsmanager&task=additem&tmpl=component';
    var req = new Request(url, {
        method: 'post',
        data: {
            'id': id,
            'value': value
        },
        onRequest: function(event, xhr) {alert('gogogo'); },
        onFailure: function(xhr) { alert('failure'.xhr); },
        onException: function(test) {alert(test); },
        onSuccess: function(data) {
            loadFieldList(data);
        }
    });
    req.send();
}

the api has transformed from 1.1x to at least one.2 -> Request now requires a single argument object that overloads all options you'll need, INCLUDING url - which was once arguments[] before.

Quite simply - slowly move the url after that right into a property from the options object:

new Request({
    url: url,
    method: 'post',
    data: {
        'id': id,
        'value': value
    },
    onRequest: function(event, xhr) {alert('gogogo'); },
    onFailure: function(xhr) { alert('failure'.xhr); },
    onException: function(test) {alert(test); },
    onSuccess: function(data) {
        loadFieldList(data);
    }
}).send();