Ok, we found the solution just yesterday!
While editing the files you probably changed the encoding.
Use notepad2 (you'll find at
www.flos-freeware.ch/notepad2.html it's the first one =) ), open the files informazioni.php, go to files => encodings and choose "utf-8".
Do it for every file you edited!
I hope this is the right solution, for the other user it worked just fine ^_^