procps w no longer listing local users

[Jan Groenewald]

On precise w no longer lists locally logged in users:

0 root@bangui:~#w
 10:46:48 up 23 min, 1 user, load average: 0.34, 0.40, 0.28
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root pts/0 tunisia.aims.ac. 10:44 0.00s 0.29s 0.00s w
0 root@bangui:~#ps auxw|grep session=ubuntu
1739 1886 0.0 0.2 395536 9692 ? Ssl 10:35 0:00 gnome-session --session=ubuntu
1739 1931 0.0 0.0 12484 324 ? Ss 10:35 0:00 /usr/bin/ssh-agent /usr/bin/dbus-launch --exit-with-session gnome-session --session=ubuntu
1739 1934 0.0 0.0 18420 488 ? S 10:35 0:00 /usr/bin/dbus-launch --exit-with-session gnome-session --session=ubuntu
root 2914 0.0 0.0 6500 888 pts/0 S+ 10:46 0:00 grep --color=auto session=ubuntu
0 root@bangui:~#

Expected output as it was on natty is something like

0 root@capetown:~#w
 10:47:16 up 41 days, 2:55, 3 users, load average: 0.00, 0.01, 0.05
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root pts/0 printserver.aims Wed07 0.00s 0.59s 0.09s ssh muizenberg
mamana pts/1 mamana-pc.local Sun13 20:59m 0.36s 0.36s -bash
root pts/2 bangui.aims.ac.z 10:47 0.00s 0.32s 0.00s w

I just rebooted some very annoyed users in a computer lab environment.

Note neither who nor users (both coreutils) show the logged in users.
We're running off LDAP, if that makes a difference.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Jan Groenewald (jan-aims)]

Adduitional information:
This is affecting me on kernel 3.2.0-25-generic but NOT on kernel 3.2.0-24-generic, where w works as expected:

0 root@nigeria:~#w
 11:12:22 up 1 day, 20:24, 3 users, load average: 1.99, 1.51, 1.61
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
wilsonle pts/0 :0 09:39 1:33m 1:42 1:33 /usr/lib/firefox/firefox http://localhost:8000/?startup_
wilsonle pts/3 :0 10:10 1.00s 3.97s 3.65s python /usr/lib/sage/local/bin/sage-ipython -i
root pts/2 muizenberg.aims. 11:09 0.00s 0.30s 0.00s w
0 root@nigeria:~#