Here’s the first weblog entry I’ve seen on problems with iTunes 5.0. However, I have read posts from a number of people who have had problems upgrading iTunes, all of them Mac users. I upgraded one of my PCs and everything went without a hitch. If I were a Mac user, I’d hold out until Apple posts an update. (I don’t think people are losing their music, rather their computers are left in a state where they can’t run iTunes, and all of their metadata appears to be gone.) Macintouch has a page about iTunes 5.0 as well.