Vpeter, It is embarrassing to me but now I found that MP3 reproduction is not possible with your build, sorry. Here an extract of the log:
18:55:09 T:1986031616 ERROR: Unable to open dll special://xbmcbin/system/
18:55:09 T:1986031616 ERROR: Previous line repeats 2 times.
18:55:09 T:1986031616 ERROR: CAudioDecoder: Unable to Init Codec while loading file smb://FRITZ-NAS/Fritz.NAS/SAMSUNG-HM500 ... /MP3/0-C/3 Doors Down/1999 The Better Life/01-Kryptonite.mp3
18:55:09 T:1986031616 WARNING: PAPlayer::QueueNextFileEx - Failed to create the decoder
18:55:09 T:1986031616 ERROR: Playlist Player: skipping unplayable item: 0, path [smb://FRITZ-NAS/Fritz.NAS/SAMSUNG-HM500JI-01/Music/MP3/0-C/3 Doors Down/1999 The Better Life/01-Kryptonite.mp3]
18:55:09 T:1986031616 ERROR: Unable to open dll special://xbmcbin/system/
18:55:09 T:1986031616 ERROR: Previous line repeats 2 times.