James Cameron wrote:
  Run memtest from the Ubuntu boot CDs for a couple of
hours, or even
 overnight. 
Already done, nothing came up, but I suppose I can do it again.
  I don't think pulseaudio does any kernel level
work, so I doubt if it
 is a direct cause of a hang.  It may be indirect if it was exercising
 something else that may cause a hang, such as some feature of ALSA.
 Describe the hang ... can the host be pinged on the network? 
That's one thing I haven't checked yet. If (when?) it happens again,
I'll be sure to check.
Thanks!
-- Darren