I rarely sync my iPhone to my computer. I prefer to download new podcasts over wifi. There seems to be a bug with multiple versions of the iPhone OS where during the download of several podcasts, something happens and you end up losing all of your music. The symptom is the iTunes application may crash and when ou restart you see "please wait updating iTunes library". After that message goes away you still have your podcasts but any songs you had are now missing. They still exist because they are taking up space still but the index seems to have gotten corrupted and as a result the music is inacessible. The only solution I have found is to sync with my computer to put all my music back on. I have seen in the Apple forums other people complaining of the same issue. Until Apple fixes this problem I am Going to download one podcast at a time and don't try and play any music or podcasts until the download completes.