gstreamer error on XO

[starsu at media.mit.edu]

Dear all,

I tested Gstreamer on OLPC-XO (build 650, B4 Machine). I tried testing  
"audiotestsrc" and some music files (e.g., ogg, mp3). However, the  
following error occurs.

gst-launch-0.10 audiotestsrc ! audioconvert ! alsasink

Setting pipeline to PAUSED ...
ERROR: Pipeline doesn't want to pause.
ERROR: from element /pipeline0/alsasink0: Resource busy or not available,
Additional debug info:
gstalsasink.c(621): gst_alsasink_open():/pipeline0/alsasink0:
Device 'default' is busy
Setting pipeline to NULL ...
FREEING Pipeline ...

Could you kindly let me know how to deal this error?

Thanks,

Sung-Hyuck