On Mon, 17 Feb 2014, Joe wrote:
Do you by any chance have pulseaudio installed? I ask because my sid workstation started doing almost exactly this a few days ago.
No. It was a server box. What you said does hint me that if I can access the physical machine there may be some clue on the screen, but then again anything there should be in one of /var/log/messages /var/log/syslog and /var/log/dmesg - yet in these I see nothing more than the previously-noted one-liner...