I do it, but same errors with aplay and mpg321
but mplayer works OK
may be that sound running in kernelspace are KO and in userspace are OK ?
I think that because I have message at startup:
Sound server informational message: Error while initializing the sound driver: device: default can't be opened for playback (No such file or directory)
I have this: http://img525.imageshack.us/my.php?image=snapshot3zc8.png
in kde kinfo