[SOLVED] valums ajax-upload broken script after xhr.send(file) - sometimes works, and sometimes does not

I searched for solution to this the better part of the day and I'm still in the dark. For a client of mine I created a simple web gallery for uploading images and I'm using valums file uploader. Till now I didn't have any problems with it on any other site I created, except miss-configuration which I solved some time ago.

So, what is the problem?

When I upload a image with filesize below 260KB it works fine. But, when I'm uploading a bigger image, it doesn't throw me back any error. I just get an empty thumbnail, because image wasn't uploaded.

When I open Chrome Console, this is what I see:

POST http://designflowstudio.com/gallery2/include/upload.php?url=uploads%2Fe558c4dfc2a0f0d60f5ebff474c97ffc&fid=7&qqfile=316267269718409738080100.jpg 403 (Forbidden) fileuploader.js:1463
POST http://designflowstudio.com/gallery2/include/upload.php?url=uploads%2Fe558c4dfc2a0f0d60f5ebff474c97ffc&fid=7&qqfile=3.jpg 403 (Forbidden) fileuploader.js:1463

On some occasions I got 413 error "Request entity too large".

Let me say that this problem really annoys me because the script works well on my local web server (apache) and on my web server. Here I can upload as may and as big images as I can find, but on the client's web server...

If anyone have time and will to help me, here is the JavaScript that I use to call the valums uploader:

     function createUploader(){
 var uploader = new qq.FileUploaderBasic({
  debug: true,
  multiple: true,
  allowedExtensions: [<?php $tmp=".";foreach($allowedExt as $ext){$tmp.="'$ext', ";}echo substr($tmp,1,strlen($tmp)-3);?>],
  button: document.getElementById('uploadDiv'),
  action: '<?php echo$home;?>include/upload.php',
  sizeLimit: <?php echo$sizeLimit;?>,
  forceMultipart: true,
  params: {'url':'uploads/<?php echo$g['path'];?>','fid':'<?php echo$g['id'];?>'},
  onSubmit: function(id, fName){$('#upload-list').append('<div id="upload-list-'+id+'" class="gallery" rel="'+fName+'"><div class="progress'+id+'"></div>');$('.progress'+id).progressbar({value:0})},
  onProgress: function(id, fName, loaded, total){
   var p = 0;
   p = parseFloat(loaded/total*100);
   if(isNaN(p)) p = '';
   $('.progress'+id).progressbar("option","value",p);
  },
  onComplete: function(id,fName,json){
   if(json.error){
    $('#upload-list-'+id).html(fName+'<br />'+json.error);
   }else{
    $('#upload-list-'+id)
     .attr("rel",json.fname)
     .html('<img class="cmd" id="deleteImg" rel="'+json.id+'" src="<?php echo$home;?>images/delete.png" title="Delete picture" /><img class="img" src="<?php echo$home;?>uploads/<?php echo$g['path'];?>/th_'+json.fname+'" /><input class="ut" type="text" name="name" value="'+json.name+'" /><input class="ud" type="text" name="desc" /><div class="cl"></div>')
     .attr("id",json.id);
   }
  },
  onError: function(id,fName,error){
   console.log(id+' '+fName+' '+error);
  }
 });
}
window.onload = createUploader;

And here is my PHP for server processing the file:

require("config.php");
require("SimpleImage.php");
ini_set("log_errors" , "1");
ini_set("error_log" , "php-errors-upload.log");
ini_set("display_errors" , "1");
/**
 * Handle file uploads via XMLHttpRequest
 */
class qqUploadedFileXhr {
    /**
     * Save the file to the specified path
     * @return boolean TRUE on success
     */
    function save($path) {
        $input = fopen("php://input", "r");
        $temp = tmpfile();
        $realSize = stream_copy_to_stream($input, $temp);
        fclose($input);

        if ($realSize != $this->getSize()){
            return false;
        }

        $target = fopen($path, "w");
        fseek($temp, 0, SEEK_SET);
        stream_copy_to_stream($temp, $target);
        fclose($target);

        return true;
    }
    function getName() {
        return $_GET['qqfile'];
    }
    function getSize() {
        if (isset($_SERVER["CONTENT_LENGTH"])){
            return (int)$_SERVER["CONTENT_LENGTH"];            
        } else {
            throw new Exception('Getting content length is not supported.');
        }
    }   
}

/**
 * Handle file uploads via regular form post (uses the $_FILES array)
 */
class qqUploadedFileForm {
    /**
     * Save the file to the specified path
     * @return boolean TRUE on success
     */
    function save($path) {
        if(!move_uploaded_file($_FILES['qqfile']['tmp_name'], $path)){
            return false;
        }
        return true;
    }
    function getName() {
        return $_FILES['qqfile']['name'];
    }
    function getSize() {
        return $_FILES['qqfile']['size'];
    }
}

class qqFileUploader {
    private $allowedExtensions = array();
    private $sizeLimit = 20485760;
    private $file;

    function __construct(array $allowedExtensions = array(), $sizeLimit = 20485760){
        $allowedExtensions = array_map("strtolower", $allowedExtensions);

        $this->allowedExtensions = $allowedExtensions;        
        $this->sizeLimit = $sizeLimit;

        $this->checkServerSettings();

        if (isset($_GET['qqfile'])) {
            $this->file = new qqUploadedFileXhr();
        } elseif (isset($_FILES['qqfile'])) {
            $this->file = new qqUploadedFileForm();
        } else {
            $this->file = false;
        }
    }

    private function checkServerSettings(){        
        $postSize = $this->toBytes(ini_get('post_max_size'));
        $uploadSize = $this->toBytes(ini_get('upload_max_filesize'));

        if ($postSize < $this->sizeLimit || $uploadSize < $this->sizeLimit){
            $size = max(1, $this->sizeLimit / 1024 / 1024) . 'M';             
            die("{'error':'increase post_max_size and upload_max_filesize to $size'}");    
        }        
    }

    private function toBytes($str){
        $val = trim($str);
        $last = strtolower($str[strlen($str)-1]);
        switch($last) {
            case 'g': $val *= 1024;
            case 'm': $val *= 1024;
            case 'k': $val *= 1024;        
        }
        return $val;
    }

    /**
     * Returns array('success'=>true) or array('error'=>'error message')
     */
    function handleUpload($uploadDirectory, $replaceOldFile = FALSE){
        chdir("../");
        if(!file_exists($uploadDirectory)){
          foreach(explode("/",$uploadDirectory) as $val){
            if(empty($val2)){$val2=$val."/";}else{$val2.=$val."/";}
            if($val<>""){if(!file_exists($val2)){mkdir($val2);}}
          }
        }

        if (!is_writable($uploadDirectory)){
            return array('error' => "Server error. Upload directory isn't writable.");
        }

        if (!$this->file){
            return array('error' => 'No files were uploaded.');
        }

        $size = $this->file->getSize();

        if ($size == 0) {
            return array('error' => 'File is empty');
        }

        if ($size > $this->sizeLimit) {
            return array('error' => 'File is too large');
        }

        $pathinfo = pathinfo($this->file->getName());
        $filename = md5($pathinfo['filename'].mt_rand());
        //$filename = md5(uniqid());
        $ext = strtolower($pathinfo['extension']);

        if($this->allowedExtensions && !in_array(strtolower($ext), $this->allowedExtensions)){
            $these = implode(', ', $this->allowedExtensions);
            return array('error' => 'File has an invalid extension, it should be one of '. $these . '.');
        }

        if(!$replaceOldFile){
            /// don't overwrite previous files that were uploaded
            while (file_exists($uploadDirectory . $filename . '.' . $ext)) {
                $filename .= rand(10, 99);
            }
        }
        if ($this->file->save($uploadDirectory .'/'. $filename . '.' . $ext)){
            global $sql_images;
            $md=md5($filename);
            $tmp=mysql_query("SELECT `order` FROM `$sql_images` WHERE `gid`='{$_REQUEST['fid']}' ORDER BY `order` DESC");
            if($tmp&&mysql_num_rows($tmp)>0){$i=mysql_result($tmp,0);$i++;}else{$i=0;}
            mysql_query("INSERT INTO `$sql_images` (`order`,`gid`,`name`,`path`) VALUES ('$i','{$_REQUEST['fid']}','{$pathinfo['filename']}','$filename.$ext')");
            $image = new SimpleImage();
            $image->load($uploadDirectory.'/'.$filename.'.'.$ext);
            $image->resizeToWidth(150);
            $image->save($uploadDirectory.'/th_'.$filename.'.'.$ext);
            return array('success'=>true,'fname'=>$filename.".".$ext,'name'=>$pathinfo['filename'],'id'=>mysql_insert_id());
        } else {
            return array('error'=> 'Could not save uploaded file.' .
                'The upload was cancelled, or server error encountered');
        }
    }
}

// list of valid extensions, ex. array("jpeg", "xml", "bmp")
$allowedExtensions = array();
// max file size in bytes
$sizeLimit = 20*1024*1024;

$uploader = new qqFileUploader($allowedExtensions, $sizeLimit);
$result = $uploader->handleUpload($_REQUEST['url']);
// to pass data through iframe you will need to encode all html tags
echo htmlspecialchars(json_encode($result), ENT_NOQUOTES);

Let me say again, all the calls to MySQL, files with require() are valid. The scripts work on two other servers, but on this one, not.

Thank you for your time and will to help.