Terrible issue with shadowbox and FLV files

Hi and thank you for attention, the only thing I can do now is to ask you help, I lost the last couple of days finding a solution myself but uncessfully, I'm really tired and pissed of from the situation.

I've installed shadowbox for Joomla and I used the same exact links from my prevuous static html site, the images works but mp4 (even flv I tried), not. It seems there is a problem loading the player.swf (I 'm using JW player), like it can't be located, and instead of it, if I click with right mouse button on the black screen an a Flash player "about".. why it loads flash player instead of JW player?? I can't figure out.
debugging the page with Chrome I've on the "bugged" box: <object type="application/x-shockwave-flash" data=nullplayer.swf">

Here's the list what I tried to make it work:

• Enabled all the file formats in the joomla plugin
• Tried the installed version and tried time by time placing in all the system/shadowbox folders the player.swf (JW player 5.1) which is working on the static site. Put it even to root/libraries folder.
• Overwritten folder by folder the shadowbox.js and shadowbox.css (where I've found it) with the one of the working static site.
• Made a lot of experiments, tried with flv and swf player, it opens only with the "qt" one but I don't want to use quicktime (the visitors doesn't have it installed).
• instead of the static site, in Joomla installation I have a flv.js file in players folder, and if I edit it with something similar I've found (around internet) for fixing the problem, the script stops working. So this file is involved in the processm and maybe the bug is inside it.
  Anyway even with swf player (there is a file swf.js) which supposed to call JW player, it doesn't work.
• Read all I found everywhere and even tried it.

May you please debug the page, click on the second photo on the right (with cars), it will display the first image, followed by an flv file (doesn't work) and with mp4 file, then other images.
http://test2.sicurezza.ru/index.php/it/servizi/ambito-residenziale-6

Thank you a lot for your support

Start by reproducing the issue at the linked Joomla page, focusing on the second photo and the FLV/MP4 entries. Inspect the generated object element and the mentioned players/flv.js, players/swf.js, shadowbox.js, and shadowbox.css files, along with the player.swf path. Done means identifying why the JW Player object receives a null data path and confirming that the video opens through the intended player.