Comment 3 for bug 1712858

This sounds like it might be the pulseaudio process getting stuck in a system call that's particular to your sound hardware/driver. Please try running 'lspci -k' and pasting the output here.

Also, the problem might not be audio-related at all. It might be some other part of your kernel that's hanging and pulseaudio is just mentioned in the syslog because it's the only one with realtime threads. That doesn't mean those threads caused the problem necessarily.

Please also try the latest live image (just boot from USB and leave it running for a while):
  http://cdimage.ubuntu.com/daily-live/current/