When messing around with lousy audio players like Amarok2, it sometimes happens that your sound system gets usurped by them when they crash (and boy do they ever crash a lot!).
The first thing to try is:
$ sudo /etc/init.d/alsa-utils restart
But that doesn’t always work, so you should see who’s holding on to who’s holding on to your sound system:
$ lsof | grep pcm
kill the processes that still have open files one at a time until you get your sound back.