Comment 15 for bug 418300

This problem appears to be caused by /dev/shm having the wrong permissions (which is also causing me a number of other problems). Running

$ sudo chmod 1777 /dev/shm

and logging out and back in fixes the problem (until the next reboot).

I am not sure why /dev/shm has the wrong permissions - /etc/init.d/mountdevsub.sh calls

domount tmpfs shmfs /dev/shm tmpfs -onosuid,nodev$SHM_OPT

This doesn't specify mode=1777, so I am not sure where this mode should be getting set (although other users confirm they do see the correct 1777 mode).