Hi Mike,

I tried to follow the suggestions on

This hints that firefox is not using PulseAudio. Maybe this  
documentation helps a bit...
https://wiki.ubuntu.com/PulseAudio

but as I'm using Debian Squeeze and not Ubuntu, it is more of a trial and error experience.

I did three things:
a) Install some more pulseaudio-related packages, among them "paman", which confirms that I have a working pulseaudio connection between host and client, from what I can tell
b) Create the /etc/asound.conf file as described on the wiki.ubuntu.com page
c) Run paplay somefile.wav to confirm that sound works on the commandline - it does.

Now, when I try to run a Youtube video in Iceweasel, it freezes and I see the following stuff on the command line:

ALSA lib pulse.c:229:(pulse_connect) PulseAudio: Unable to connect: Zeitüberschreitung

ALSA lib pcm_hw.c:1401:(_snd_pcm_hw_open) Invalid value for card

Next up: Trying to follow John A. Sullivan III's reply.

Kind Regards,
Stefan