Paolo,
I responded to your Private Message earlier, but wanted to make sure the answer was captured here as well...
Can you check the on the Basic Checks area of the first screen that 'cURL' was enabled? If it is enabled, then please go to Site -> System Information and then the PHP Information tab. Do a search for "disable_functions". If it's there, there should be a comma-separated list of functions that PHP is not allowed to execute. Look for "curl_exec". If that's in the list, you'll need to contact your host to lift the restriction on that function. curl_exec is required for a lot of communication with Facebook as well as it's required to use the Autotune configuration tool.
Hope that helps get you started, but if you still run into issues, please let us know!
Alex