HDX: disrupted replay of iTunes library

My HDX scans and replays most downloaded files from iTuwith quite reliably. Some albums, however, appear to have scanned ok but not all tracks play fully. Replay suddenly ends and the machine cuts to the next track. iTunes willreplay the tracks on my computer with no problem. Tracks are stored on a NAS which is connected to the HDX via a gigabit switch and cat5 cable. Any ideas?