X11 crashes after upgrade to Aramo

Hi all

After upgrading my Trisquel install to Aramo recently (the do-release-upgrade would not go through because of some dependency issues, so I upgraded via aptitude instead), I am experiencing fairly random (sometimes upon sending a mail with Icedove, other times when opening a pdf with Atril) X11 server crashes which force a user logout.

Digging a bit in /var/log/syslog shows repeated

pulseaudio[3543]: X11 I/O error handler called
pulseaudio[3543]: X11 I/O error exit handler called, preparing to tear down X11 modules

messages at the exact timestamps when I get logged out.

Any ideas on how to prevent this?