screenshot, upload and set as feature for link posts

Hi I have found this code to upload and set as feature the image of the links. This is my modified code: http://pastebin.com/3CP4kr82

I have tested with this and not work:

$thumb_url = 'http://s.wordpress.com/mshots/v1/clarin.com?w=400';

And test with this and it works:

$thumb_url = 'http://i1.ytimg.com/vi/ZWaX1g_2SSQ/default.jpg';

1. What can be happening?

Another doubt it that the code not work with the plugin WPUF but works with wordpress backend. I think that the plugin WPUF not uses the action "save_post".

2. Exist a way to add this action to the plugin, to test if works?

Thanks and greetings