Hi Michele84,
Your XML looks OK, to me at least. And as it works locally, it should work (and does as you wrote) online, too.
I see you have two files on that page - an SWF and a MP3. Could it be your MP3 is not just a loop, but a bigger piece? SWFs can be big sometimes, the same for MP3s (which sometimes take up to 1 MB per minute, unless you know how to compress them better) ...
Perhaps it is just a connection problem? (Are you on broadband?) - Is the sound file music or speech? Can I see it online somewhere?