I discovered that /var/log/syslog reports:
Gdk-WARNING: gnome-session: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.#012
On searching for bugs with similar text, I found Bug #583525, in which a commenter noted that the bug could be produced just with xclock. I also find that running xclock restarts the X server and reverts me to the login screen.
I have attempted to follow the instructions in http://wiki.ubuntu.com/DebuggingProgramCrash, but despite installing xserver-xorg-core-dbg, I don't have a version of xclock that was compiled with debugging symbols. I also couldn't manage to install a debug package for qtnx (following the instructions for a package for which ####-dbg does not exist). However, I have produced an strace of both qtnx and xclock.
I discovered that /var/log/syslog reports:
Gdk-WARNING: gnome-session: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.#012
On searching for bugs with similar text, I found Bug #583525, in which a commenter noted that the bug could be produced just with xclock. I also find that running xclock restarts the X server and reverts me to the login screen.
I have attempted to follow the instructions in http:// wiki.ubuntu. com/DebuggingPr ogramCrash, but despite installing xserver- xorg-core- dbg, I don't have a version of xclock that was compiled with debugging symbols. I also couldn't manage to install a debug package for qtnx (following the instructions for a package for which ####-dbg does not exist). However, I have produced an strace of both qtnx and xclock.