wpthumb not working in production

[mocheaz]

I created a function that work well on my local machine but not in production server.

Here my code:

function video_thumb($pic){
    $w = $pic[1];
    $h = $pic[2];
    $image = new WP_Thumb($pic[0], array(
        'width' => $w,
        'height' => $h,
        'cache' => true,
        'return' => 'url',
        'jpeg_quality' => 80,
        'watermark_options' => array(
            'mask' => 'http://unitedwithisrael.org/wp-content/themes/uwi2013/images/play.png',
            'position' => 'top,left',
            'padding' => 0)
        )
    );

    return $image->getCacheFileUrl();
}

Any idea what's wrong?