I'm using the Facebook Javascript SDK to post on my page, i've already read something about this here: Facebook feed dialog: allow user to select destination page or group so I've been using this code so far:

$("button#shareOn").on('click',function(event){
    event.preventDefault();

    var _parentForm=$(this).parents('form:first');
    var _pageSelect=_parentForm.find("select[name='pagesList']");
    var _pID=_parentForm.find("#pID").attr('value');
    var _vURL=_parentForm.find("#_vURL").attr('value');

    FB.ui({
        app_id:app_id,
        method: 'feed',
        from: _pageSelect.val(),
        name: 'Title',
        caption: 'Subtitle - 26/02/2013',
        description: 'My text',
        link: _vURL,
    },function(response){
        console.log(response);
    });

});

Where _pageSelect.val() is the ID of the page in which I'm trying to post, _vURL is the url ( youtube link ) which I want to share... The problem is that when I click on the button, a window opens up, but's actually blank.

By opening Google Chrome's dev console, sometimes I see a 500 Internal Server error related to that window and sometimes it only comes up totally empty, but I can't figure out what is actually causing it.
I've also tried urlencode the url from PHP or encodeURIComponent from Javascript, but nothing as changed at all.

Sometimes the window comes up only with Title, Subtitle and Description, so I guess the link should be the error, but I knew that Facebook JS SDK used to write Link not properly formatted or something like API error (100).

UPDATE

It seems that Feed dialog has started collaborating, but still not working as expected. This is the updated code:

$("button#shareOn[name='shareVideo']").on('click',function(event){
    event.preventDefault();

    var _parentForm=$(this).parents('form:first');
    var _pageSelect=_parentForm.find("select[name='pagesList']");
    var _pID=_parentForm.find("#pID").attr('value');
    var _vURL=_parentForm.find("#_vURL").attr('value');
    var options={
        app_id:app_id,
        method:'feed',
        from:_pageSelect.val(),
        link:_vURL,
        caption:'test'
    }

    console.log(options);

    FB.ui( options, function(response){});

});

The window is opening, but sometimes it's blank and sometimes shows a link, which is not the url of the video, but it's just www.youtube.com. I've been trying with the Facebook URL Debugger and it's showing me that the URL which I'm using is actually right. But feed dialog just doesn't work

So, I've got the answer, which isn't really what I was expecting, but at least it works. As the Facebook docs aren't pointing to this, I've found the sharer method, which I call in a Javascript function. So, this is the code:

$("button#shareOn[name='shareVideo']").on('click',function(event){
    event.preventDefault();

    var _parentForm=$(this).parents('form:first');
    var _pageSelect=_parentForm.find("select[name='pagesList']");
    var _pID=_parentForm.find("#pID").attr('value');
    var _vURL=_parentForm.find("#_vURL").attr('value');
    var leftPosition, topPosition;
    var windowFeatures = "status=no,height=" + 400 + ",width=" + 300 + ",resizable=yes,left=" + leftPosition + ",top=" + topPosition + ",screenX=" + leftPosition + ",screenY=" + topPosition + ",toolbar=no,menubar=no,scrollbars=no,location=no,directories=no";

    leftPosition = (window.screen.width / 2) - ((300 / 2) + 10);
    topPosition = (window.screen.height / 2) - ((400 / 2) + 50);

    window.open('http://www.facebook.com/sharer.php?u='+encodeURIComponent(_vURL),'sharer', windowFeatures);
    return false;
});

By the way, I don't like this method, but it seems like the only way to accomplish what i was trying to do. Now I just need to know how to get the result of the sharing function ( if the post was shared or not ).

Hope this will help someone :)