For some reason GStreamer on my laptop lost its settings and changing the settings with gstreamer-properties was also not easy. The default settings were gone and I couldn't find out how to retrieve them.
Some applications thought they were talking to aRTS, but in reality were talking in some strange way with Alsa. This resulted in very poor sound quality. I almost started to think a recently ripped CD had some new copyright "protection" on it.
Anyway, I got fed up with this situation and started looking for a solution. Running "gst-register-0.8" solved all my problems. Even with the sound quality! Very strange.