Ich hab dann hierzu doch noch was gefunden, allerdings sind da dann mal die admins gefordert:
ZitatAlles anzeigenThis usually happens when the web server doesn't know what content type a .mp4 or mp3 file is and so gives the generic one of text/plain. When the browsers see text/plain they don't download it but display the "text", which in reality is just all the garbage you see. I just checked and it appears that this is happening in this case.
To fix that you need to tell Apache what MIME content type to send for the files. Create a .htaccess file in the root directory of the website with the following in it
AddType audio/mpeg mp3
AddType audio/mp4 mp4
It's possible that your web host may not let you add types in this way, in which case you'll have to contact them.