There is a bug in Qt Mobility 1.1.1 which prevents audio playback using gstreamer. It occurs on desktop Linux and on Maemo5. The bug is fixed in the 1.1 git branch.

Would it be possible to get that version into Extras-devel? It's even enough to replace plugins/mediaservice/libqgstengine.so. Having no audio playback is (for some apps) a major blocker.