I'm not entirely certain of this, but as no one has offered anything else I thought I'd throw it up.
Sometimes firefox/flashplayer seems to hog the OSS sound device which then blocks other programs trying to use alsa. You could try disabling OSS completely with
Code:
rmmod snd_seq_oss
rmmod snd_pcm_oss
rmmod snd_mixer_oss
If you find it helps, then you can blacklist them permanently, assuming you don't need OSS for anything else. Alternatively, you could try starting firefox with the aoss wrapper, but I'm not sure if that'll work.
Anyway, have a go and see how you get on.
