hi, i bought a new ipod nano 2 weeks ago, and it works perfectly, apart from it will not update, i'm using a mac laptop, every time i try to update, it says it cannot because it contains files that are in use by another program. it says this even when i close down all other programs and i only have itunes running, and ive tried restoring it to factory settings and it still says the same thing, anyone got any other ideas?