What happens if you play the flac files from the PC rather than the NAS is the problem the same? (What UPnP Server software are you using and where is it located PC and/or NAS)

What I am thinking is rule out the NAS/Flac combination being and issue as I assume from your comments that NAS/MP3 are fine.

I have seen this type of problem before where one type of audio file works fine and another does not, but cannot remember what are the key issues that can cause it.

It may be worth reviewing the Media Streamer bugs at https://garage.maemo.org/projects/mediastreamer/ for some clues but whilst Nokia have updated Media Streamer for OS2008 they have not been keeping the data topical/aligned at garage.maemo.org?

Another possibility is to contact the Project Admin visa.smolander @nospam@ nokia.com who has been very helpful in the past and may have some ideas.

Continue to post your experiences at ITT and we will try and help you.