sound from thin clients playing on server speakers

[dbclinton]

Hi,
My server has been experiencing trouble with alsamixer (it won't load
and returns "PULSEAUDIO: Unable to connect: Connection refused
alsamixer: function snd_ctl_open failed for default: Connection
refused"). Sound Recorder similarly doesn't load. And don't even think
about Skype. Weirdly, the clients can load Sound Recorder (though it
won't actually record).
However, the problem I'm focusing on now is the misdirection of thin
client sound. As I type this, the many (and strange) sounds from my
kid's session of Scratch on his client are coming through my (server's)
speakers - and not through his!
Any ideas?
David