jQuery Uploadify doesn't send any request to upload.php

I have following problem with uploadify and I'm planing to use iframe. I already lost few hours without any result.

Here is my code;

$('#file').uploadify({
    'uploader'      : 'includes/js/uploadify/uploadify.swf',
    //'checkScript'     : 'includes/ajax/sales/upload.php',
    'script'        : 'includes/ajax/sales/upload.php',
    'cancelImg'     : 'includes/js/uploadify/cancel.png',
    'folder'        : 'uploads/items/',
    'multi'         : false,
    'fileExt'       : '*.xls;*.txt;*.csv',
    'fileDesc'      : 'Allowed Files',
    'buttonText'    : 'Files',
    'fileDataName'  : 'file',
    'method'        : 'post',
    'scriptData'    : {'required1':'<?php echo $required1; ?>','required2':'<?php echo $required2; ?>'},
    'sizeLimit'     : 1024 * 1024 * 5, // 5MB
    'onError'       : function (event,ID,fileObj,errorObj) {
          alert(errorObj.type + ' ERROR: ' + errorObj.info);
        },      
    'onComplete'    : function(event, ID, fileObj, response, data) {
          alert('Success!!');
        }
});

My upload.php works perfectly. I have tried my upload.php script just to see if it will work or not and it did work as expected.
I decided to add a small code to create a log file just to see if my upload.php has been executed or not. If I don't use checkScript, then there are no logs. If I use checkScript then there are logs and I can see uploadify sending request with using POST to my upload.php script with FireBug.
Even though it is not sending any request to upload.php, it is still showing Success!! alert.
Simply 'script' doesn't send absolutely any request to upload.php but strangely if I use upload2.php (file doesn't exist) then it gives me 404 error.

I'm not sure if this is a bug but it kinda seems to me like a bug considering I did follow documentation, my upload.php works as expected, my folder permissions are 777 still doesn't work.

I will be glad if anyone could point out what is this problem and how to solve it.

Solution

I don't know what is causing this problem, maybe browser, add-on or flash related problem. It just doesn't upload anything at all.

So I downloaded V3.0.0 (BETA) version and everything works as expected.