Occasional ajax response error { readyState=0, status=0, statusText="error"} using jquery

I have run into a problem with the AJAX response using jquery (and coldfusion serverside). Sometimes it works and sometimes it doesn't. When I test the serverside component calling it directly - it always works, so I guess the problem is with the ajax response. I get the serverurl, directly from the server - so it shouldn't be a cross-domain issue. I just show and hide div-tags so it shouldn't be about relocating the url before the ajax response has been processed. I am pulling out a lot of hair over this.

The code for the addTask method:

function addTask(){
    var priority = $('#ff-add-task-priority').length > 0 ? $('#ff-add-task-priority').val() : 0;
        
    $.ajax({
        url: settings.server+'/c/Tasks.cfc?method=addTask',
        data: {
            userid: settings.userid, 
            taskname: $('#ff-add-task-name').val(),
            tasknote: $('#ff-add-task-note').val(),
            completed: $('#ff-add-task-completed').val(),
            priority: priority,
        },
        type: 'POST',
        dataType: 'json',
        success: function(response) {
            var output = addRow(response, $('#ff-add-task-name').val(), 0, 0);
            $('#data-list-tasks').append(output);
            
            $('#main').children().addClass('hide');
            $('#section-list-tasks').removeClass('hide');
            resetForm($('#add-task-form'));
            //route('#section-list-tasks');
        },
        error: function(ErrorMsg) {
            console.log('Error', ErrorMsg);
        }
    });
}

Firebug output shows that the AJAX calls works sometimes and sometimes it fails.:

POST http://dev.wedoolist.com/c/Tasks.cfc?method=addTask jquery.min.js (linje 2) Error Object { readyState=0, status=0, statusText="error"} #secti...t-tasks (linje 124)
POST http://dev.wedoolist.com/c/Tasks.cfc?method=getTasks 200 OK 152ms jquery.min.js (linje 2)
POST http://dev.wedoolist.com/c/Tasks.cfc?me