I bought my z1 from this friend of mine who runs an audio video shop in florida and he had this unit as a display model for like a month or so and sold it to me for a really good price, but so i far i found out that the z1 is not playing DVD's. i've tried many store bought dvd's but its says unreadable disk. As far as my friend says, he tested the unit fully and it was in excellent working condition. So now the problem persists and i need some info as to what can be wrong with it. It plays all the audio cd's, mp3, plays my ipod and all the navigation features but its only the DVDs that are not