I have a M1000, R1000, and M2000. The M1000 and R1000 are wireless; the M2000 is wired. All songs play fine on the M2000, but some songs won't play on the wireless units. My Firefly server is running on a Vista PC that is wired to a Zyxel P330 set to bridge to my router. PC can surf and stream to the M2000, but songs won't go to the M1000 and R1000--some songs play and others don't.