Bug#477484: gdm does not start with high resolutions (e.g. 1280x1024)

[ant+bdo at hsg-kl.de]

Package: gdm
Version: 2.20.5-1
Severity: grave
Justification: renders package unusable

Hello,

when I configure X.org for a high resolution (e.g. 1280x1024), gdm does not
start. It logs the following to syslog:

Apr 23 12:19:10 c02pc gdm[9528]: WARNING: Xinerama active, but <= 0
screens?

I am using the default gdm-config and my xorg.conf is pasted below.
When I change 'Modes "1024x768"' to 'Modes "1280x1024"' gdm does not start.

xorg.conf:

Section "Files"
EndSection

Section "InputDevice"
        Identifier      "Generic Keyboard"
        Driver          "kbd"
        Option          "CoreKeyboard"
        Option          "XkbRules"      "xorg"
        Option          "XkbModel"      "pc105"
        Option          "XkbLayout"     "de"
EndSection

Section "InputDevice"
        Identifier      "Configured Mouse"
        Driver          "mouse"
        Option          "CorePointer"
        Option          "Device"                "/dev/input/mice"
        Option          "Protocol"              "ImPS/2"
        Option          "Emulate3Buttons"       "true"
EndSection

Section "Device"
        Identifier      "Generic Video Card"
        Driver          "vesa"
EndSection

Section "Monitor"
        Identifier      "Generic Monitor"
        Option          "DPMS"                                                 
        HorizSync       28-49
        VertRefresh     43-72
EndSection

Section "Screen"
        Identifier      "Default Screen"
        Device          "Generic Video Card"
        Monitor         "Generic Monitor"
        DefaultDepth    24
        SubSection "Display"
                Modes           "1024x768"
        EndSubSection
EndSection

Section "ServerLayout"
        Identifier      "Default Layout"
        Screen          "Default Screen"
        InputDevice     "Generic Keyboard"
        InputDevice     "Configured Mouse"
EndSection

-- System Information:
Debian Release: lenny/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: i386 (i686)

Kernel: Linux 2.6.24-1-686 (SMP w/2 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages gdm depends on:
ii  adduser                3.107             add and remove users and groups
ii  debconf [debconf-2.0]  1.5.20            Debian configuration management sy
ii  fluxbox [x-window-mana 1.0.0+deb1-6      Highly configurable and low resour
ii  gksu                   2.0.0-5           graphical frontend to su
ii  gnome-session          2.22.0-2          The GNOME 2 Session Manager
ii  gnome-terminal [x-term 2.22.1-1          The GNOME 2 terminal emulator appl
ii  libart-2.0-2           2.3.20-1          Library of functions for 2D graphi
ii  libatk1.0-0            1.22.0-1          The ATK accessibility toolkit
ii  libattr1               1:2.4.41-1        Extended attribute shared library
ii  libc6                  2.7-10            GNU C Library: Shared libraries
ii  libcairo2              1.4.14-1          The Cairo 2D vector graphics libra
ii  libdbus-1-3            1.1.20-1          simple interprocess messaging syst
ii  libdbus-glib-1-2       0.74-1            simple interprocess messaging syst
ii  libdmx1                1:1.0.2-2         X11 Distributed Multihead extensio
ii  libfontconfig1         2.5.0-2           generic font configuration library
ii  libfreetype6           2.3.5-1+b1        FreeType 2 font engine, shared lib
ii  libglade2-0            1:2.6.2-1         library to load .glade files at ru
ii  libglib2.0-0           2.16.1-2          The GLib library of C routines
ii  libgnomecanvas2-0      2.20.1.1-1        A powerful object-oriented display
ii  libgtk2.0-0            2.12.9-2          The GTK+ graphical user interface
ii  libpam-modules         0.99.7.1-6        Pluggable Authentication Modules f
ii  libpam-runtime         0.99.7.1-6        Runtime support for the PAM librar
ii  libpam0g               0.99.7.1-6        Pluggable Authentication Modules l
ii  libpango1.0-0          1.20.2-2          Layout and rendering of internatio
ii  librsvg2-2             2.22.2-2          SAX-based renderer library for SVG
ii  librsvg2-common        2.22.2-2          SAX-based renderer library for SVG
ii  libselinux1            2.0.59-1          SELinux shared libraries
ii  libwrap0               7.6.q-15          Wietse Venema's TCP wrappers libra
ii  libx11-6               2:1.0.3-7         X11 client-side library
ii  libxau6                1:1.0.3-2         X11 authorisation library
ii  libxdmcp6              1:1.0.2-2         X11 Display Manager Control Protoc
ii  libxext6               2:1.0.4-1         X11 miscellaneous extension librar
ii  libxi6                 2:1.1.3-1         X11 Input extension library
ii  libxinerama1           2:1.0.3-1         X11 Xinerama extension library
ii  libxml2                2.6.31.dfsg-2     GNOME XML library
ii  lsb-base               3.1-24            Linux Standard Base 3.1 init scrip
ii  metacity [x-window-man 1:2.22.0-1        A lightweight GTK2 based Window Ma
ii  rxvt-unicode-ml [x-ter 9.02-1            multi-lingual terminal emulator wi
ii  xterm [x-terminal-emul 234-1             X terminal emulator
ii  zlib1g                 1:1.2.3.3.dfsg-12 compression library - runtime

Versions of packages gdm recommends:
ii  dialog           1.1-20080316-1          Displays user-friendly dialog boxe
ii  gdm-themes       0.5.1                   Themes for the GNOME Display Manag
ii  whiptail         0.52.2-11.2             Displays user-friendly dialog boxe
ii  xnest            2:1.3.0.0.dfsg-12lenny2 Nested X server
ii  xserver-xorg     1:7.2-5                 the X.Org X server
ii  zenity           2.22.1-1                Display graphical dialog boxes fro

-- debconf information:
  gdm/daemon_name: /usr/bin/gdm
* shared/default-x-display-manager: gdm