chr1s@chris-desktop:~/system-tools-backends-2.6.0$ ./test-backends.in UsersConfig
UsersConfig
================================
ARRAY = [
  ARRAY = [
    test
    $1$46CI4C7H$eZmkCIqTCrFfMKUclxj.u/
    1002
    1007
    ARRAY = [
      Test User
      
      
      
      
    ]
    /home/test
    /bin/sh
  ]
  ARRAY = [
    bin
    *
    2
    2
    ARRAY = [
      bin
      
      
      
      
    ]
    /bin
    /bin/sh
  ]
  ARRAY = [
    nobody
    *
    65534
    65534
    ARRAY = [
      nobody
      
      
      
      
    ]
    /nonexistent
    /bin/sh
  ]
  ARRAY = [
    lp
    *
    7
    7
    ARRAY = [
      lp
      
      
      
      
    ]
    /var/spool/lpd
    /bin/sh
  ]
  ARRAY = [
    gdm
    !
    109
    118
    ARRAY = [
      Gnome Display Manager
      
      
      
      
    ]
    /var/lib/gdm
    /bin/false
  ]
  ARRAY = [
    irc
    *
    39
    39
    ARRAY = [
      ircd
      
      
      
      
    ]
    /var/run/ircd
    /bin/sh
  ]
  ARRAY = [
    list
    *
    38
    38
    ARRAY = [
      Mailing List Manager
      
      
      
      
    ]
    /var/list
    /bin/sh
  ]
  ARRAY = [
    messagebus
    !
    103
    109
    ARRAY = [
      
      
      
      
      
    ]
    /var/run/dbus
    /bin/false
  ]
  ARRAY = [
    sys
    *
    3
    3
    ARRAY = [
      sys
      
      
      
      
    ]
    /dev
    /bin/sh
  ]
  ARRAY = [
    j0ey
    $1$OSX77$VoC5kR3Qc8xrBeoxJXILd1
    1001
    1001
    ARRAY = [
      Joanne Fry
      
      
      
      
    ]
    /home/j0ey
    /bin/bash
  ]
  ARRAY = [
    haldaemon
    !
    107
    115
    ARRAY = [
      Hardware abstraction layer
      
      
      
      
    ]
    /home/haldaemon
    /bin/false
  ]
  ARRAY = [
    gnats
    *
    41
    41
    ARRAY = [
      Gnats Bug-Reporting System (admin)
      
      
      
      
    ]
    /var/lib/gnats
    /bin/sh
  ]
  ARRAY = [
    klog
    !
    102
    103
    ARRAY = [
      
      
      
      
      
    ]
    /home/klog
    /bin/false
  ]
  ARRAY = [
    polkituser
    *
    113
    126
    ARRAY = [
      PolicyKit
      
      
      
      
    ]
    /var/run/PolicyKit
    /bin/false
  ]
  ARRAY = [
    avahi
    !
    105
    112
    ARRAY = [
      Avahi mDNS daemon
      
      
      
      
    ]
    /var/run/avahi-daemon
    /bin/false
  ]
  ARRAY = [
    proxy
    *
    13
    13
    ARRAY = [
      proxy
      
      
      
      
    ]
    /bin
    /bin/sh
  ]
  ARRAY = [
    pulse
    *
    112
    120
    ARRAY = [
      PulseAudio daemon
      
      
      
      
    ]
    /var/run/pulse
    /bin/false
  ]
  ARRAY = [
    avahi-autoipd
    !
    104
    111
    ARRAY = [
      Avahi autoip daemon
      
      
      
      
    ]
    /var/lib/avahi-autoipd
    /bin/false
  ]
  ARRAY = [
    games
    *
    5
    60
    ARRAY = [
      games
      
      
      
      
    ]
    /usr/games
    /bin/sh
  ]
  ARRAY = [
    libuuid
    !
    114
    127
    ARRAY = [
      
      
      
      
      
    ]
    /var/lib/libuuid
    /bin/sh
  ]
  ARRAY = [
    hplip
    !
    108
    7
    ARRAY = [
      HPLIP system user
      
      
      
      
    ]
    /var/run/hplip
    /bin/false
  ]
  ARRAY = [
    www-data
    *
    33
    33
    ARRAY = [
      www-data
      
      
      
      
    ]
    /var/www
    /bin/sh
  ]
  ARRAY = [
    statd
    !
    110
    65534
    ARRAY = [
      
      
      
      
      
    ]
    /var/lib/nfs
    /bin/false
  ]
  ARRAY = [
    chr1s
    $1$d4FGK$ZsDQ7amZ9FOoNaoedLcUc/
    1000
    1000
    ARRAY = [
      Chris Coulson
      
      
      
      
    ]
    /home/chr1s
    /bin/bash
  ]
  ARRAY = [
    cupsys
    !
    106
    114
    ARRAY = [
      
      
      
      
      
    ]
    /home/cupsys
    /bin/false
  ]
  ARRAY = [
    mail
    *
    8
    8
    ARRAY = [
      mail
      
      
      
      
    ]
    /var/mail
    /bin/sh
  ]
  ARRAY = [
    root
    
    0
    0
    ARRAY = [
      root
      
      
      
      
    ]
    /root
    /bin/bash
  ]
  ARRAY = [
    daemon
    *
    1
    1
    ARRAY = [
      daemon
      
      
      
      
    ]
    /usr/sbin
    /bin/sh
  ]
  ARRAY = [
    backup
    *
    34
    34
    ARRAY = [
      backup
      
      
      
      
    ]
    /var/backups
    /bin/sh
  ]
  ARRAY = [
    ntp
    *
    115
    128
    ARRAY = [
      
      
      
      
      
    ]
    /home/ntp
    /bin/false
  ]
  ARRAY = [
    uucp
    *
    10
    10
    ARRAY = [
      uucp
      
      
      
      
    ]
    /var/spool/uucp
    /bin/sh
  ]
  ARRAY = [
    sync
    *
    4
    65534
    ARRAY = [
      sync
      
      
      
      
    ]
    /bin
    /bin/sync
  ]
  ARRAY = [
    man
    *
    6
    12
    ARRAY = [
      man
      
      
      
      
    ]
    /var/cache/man
    /bin/sh
  ]
  ARRAY = [
    syslog
    !
    101
    102
    ARRAY = [
      
      
      
      
      
    ]
    /home/syslog
    /bin/false
  ]
  ARRAY = [
    news
    *
    9
    9
    ARRAY = [
      news
      
      
      
      
    ]
    /var/spool/news
    /bin/sh
  ]
  ARRAY = [
    dhcp
    !
    100
    101
    ARRAY = [
      
      
      
      
      
    ]
    /nonexistent
    /bin/false
  ]
  ARRAY = [
    sshd
    !
    111
    65534
    ARRAY = [
      
      
      
      
      
    ]
    /var/run/sshd
    /usr/sbin/nologin
  ]
]
ARRAY = [
  /bin/csh
  /bin/bash
  /usr/bin/tcsh
  /usr/bin/screen
  /bin/sh
  /bin/dash
  /bin/tcsh
  /bin/rbash
  /bin/false
]
1
1000
60000
/home/
/bin/bash
-1


Have a good day!

I've got exactly the same issue as Marcus. I can't add or delete any users, and I get the following spat out in the terminal:

(users-admin:21721): Liboobs-CRITICAL **: create_dbus_struct_from_user: assertion `(login && password && homedir && shell)' failed

(users-admin:21721): Liboobs-CRITICAL **: Not committing due to inconsistencies in the configuration, this reflects a bug in the application

I've attached my output of test-backends UsersConfig. In my case, all users have a valid shell.

I'm also experiencing the other symptoms here (no shells appear in drop-down list when I attempt to add a user).

This is on Ubuntu Hardy. Some version info:
chr1s@chris-desktop:~/system-tools-backends-2.6.0$ apt-cache policy gnome-system-tools
gnome-system-tools:
  Installed: 2.22.0-0ubuntu9
  Candidate: 2.22.0-0ubuntu9
  Version table:
 *** 2.22.0-0ubuntu9 0
        500 http://archive.ubuntu.com hardy/main Packages
        100 /var/lib/dpkg/status
chr1s@chris-desktop:~/system-tools-backends-2.6.0$ apt-cache policy system-tools-backends
system-tools-backends:
  Installed: 2.6.0-0ubuntu7
  Candidate: 2.6.0-0ubuntu7
  Version table:
 *** 2.6.0-0ubuntu7 0
        500 http://archive.ubuntu.com hardy/main Packages
        100 /var/lib/dpkg/status
chr1s@chris-desktop:~/system-tools-backends-2.6.0$ apt-cache policy liboobs-1-4
liboobs-1-4:
  Installed: 2.22.0-0ubuntu1
  Candidate: 2.22.0-0ubuntu1
  Version table:
 *** 2.22.0-0ubuntu1 0
        500 http://archive.ubuntu.com hardy/main Packages
        100 /var/lib/dpkg/status
chr1s@chris-desktop:~/system-tools-backends-2.6.0$ apt-cache policy dbus
dbus:
  Installed: 1.1.20-1ubuntu1
  Candidate: 1.1.20-1ubuntu1
  Version table:
 *** 1.1.20-1ubuntu1 0
        500 http://archive.ubuntu.com hardy/main Packages
        100 /var/lib/dpkg/status

