There are two possible cause as far as I know.
- If you have set the sleep timer, playback will stop at designated time.
- When the CPU usage is high, the playback will be interrupted

Your case is most like the second one. Currently I don't have solution for this. I am trying to figure out a way to set the process priority to high, but I am not sure this is doable through API.

I fount out from TOP command that "pulseaudio" has --high-priority switch. Since symfonie uses QT phonon framework for playback, I don't think symofnie getting this priority benefit.

I am hoping any expert here can explain how to do this for application in Maemo.

There's a walk around for this. Whenever the playback stops, pause the playback for a few second. Once the program catches up its breathe, it will play again.