in the last two days, when i make something in garageband and i want to export to disk. before i would choose my desktop and after normalizing and converting...it would put a mp3 on my desktop. recently when i do this, it normalizes the track...but it just stops after that....no mp3 on my desktop....i have to send it to itunes now and then pull it out of itunes to have an mp3....what is going on?