I just found a (possible) quirk in the iPhone DPS app. I have an INXS album which I bought on iTunes long ago. The album is called Switch and it has a "bonus" track titled Let's Ride. I tried to play it through DPS on the iPhone and it says the track is DRM protected and won't play it. It plays via the normal iPhone music app and it also plays fine on iTunes (Windows 7) with DPS running.
How does DPS determine that DRM is present and why does the song play with DPS on a computer but not on an iPhone?