* Purchased tracks randomly grey out and become non-playable.* This 1000 times. I've been through three iPhones, and continue to be baffled why some of my mus

* Purchased tracks randomly grey out and become non-playable.* This 1000 times. I've been through three iPhones, and continue to be baffled why some of my music becomes unplayable. I solve by syncing (again and again...), navigating endless menus and changing random values in a vain attempt to find the problem and then hoping, and praying that next time I'm in my car, all my music will be available.