are you shure, you have url_fopen enabled in your server ??
try to create an info.php file upload it to your server and have a look at the second block it gives you when calling the file
create a new php file, call it info.php
include just this code:
and save the file to your root folder, then call the file
http://yoursite/info.php
look at the second block it gives you for allow_url_rewrite and allow_url_fopen ON
but it could be an permissions ( CHmod) problem aswell