C’est moi qui ai jouer le bourin en essayant d’ajouter des résolutions à la main. 
Voila le Xorg.0.log :
[code]X.Org X Server 1.7.7
Release Date: 2010-05-04
X Protocol Version 11, Revision 0
Build Operating System: Linux 2.6.37-trunk-amd64 x86_64 Debian
Current Operating System: Linux alexis-pc 2.6.32-5-amd64 #1 SMP Thu Nov 3 03:41:26 UTC 2011 x86_64
Kernel command line: BOOT_IMAGE=/boot/vmlinuz-2.6.32-5-amd64 root=UUID=afebc585-7c41-4094-83e8-1375794fa59d ro quiet
Build Date: 18 February 2011 08:27:24PM
xorg-server 2:1.7.7-13 (Cyril Brulebois kibi@debian.org)
Current version of pixman: 0.16.4
Before reporting problems, check http://wiki.x.org
to make sure that you have the latest version.
Markers: (–) probed, () from config file, (==) default setting,
(++) from command line, (!!) notice, (II) informational,
(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: “/var/log/Xorg.0.log”, Time: Sat Mar 10 18:23:26 2012
(==) Using config file: “/etc/X11/xorg.conf”
(==) Using system config directory “/usr/share/X11/xorg.conf.d”
(==) ServerLayout “Layout0”
() |–>Screen “Screen0” (0)
() | |–>Monitor “Monitor0”
() | |–>Device “Device0”
() |–>Input Device “Keyboard0”
() |–>Input Device “Mouse0”
(==) Automatically adding devices
(==) Automatically enabling devices
(WW) The directory “/usr/share/fonts/X11/cyrillic” does not exist.
Entry deleted from font path.
(==) FontPath set to:
/usr/share/fonts/X11/misc,
/usr/share/fonts/X11/100dpi/:unscaled,
/usr/share/fonts/X11/75dpi/:unscaled,
/usr/share/fonts/X11/Type1,
/usr/share/fonts/X11/100dpi,
/usr/share/fonts/X11/75dpi,
/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType,
built-ins
(==) ModulePath set to “/usr/lib/xorg/modules”
(**) Extension “Composite” is enabled
(WW) AllowEmptyInput is on, devices using drivers ‘kbd’, ‘mouse’ or ‘vmmouse’ will be disabled.
(WW) Disabling Keyboard0
(WW) Disabling Mouse0
(II) Loader magic: 0x7c8aa0
(II) Module ABI versions:
X.Org ANSI C Emulation: 0.4
X.Org Video Driver: 6.0
X.Org XInput driver : 7.0
X.Org Server Extension : 2.0
(++) using VT number 8
(–) PCI: (0:0:1:3) 10de:0753:1043:82f2 nVidia Corporation MCP78S [GeForce 8200] Co-Processor rev 162, Mem @ 0xf9e80000/524288
(–) PCI:*(0:2:0:0) 10de:06e4:0000:0000 nVidia Corporation G98 [GeForce 8400 GS] rev 161, Mem @ 0xfd000000/16777216, 0xd0000000/268435456, 0xfa000000/33554432, I/O @ 0x0000ec00/128, BIOS @ 0x???/131072
(II) Open ACPI successful (/var/run/acpid.socket)
(II) LoadModule: “extmod”
(II) Loading /usr/lib/xorg/modules/extensions/libextmod.so
(II) Module extmod: vendor="X.Org Foundation"
compiled for 1.7.7, module version = 1.0.0
Module class: X.Org Server Extension
ABI class: X.Org Server Extension, version 2.0
(II) Loading extension SELinux
(II) Loading extension MIT-SCREEN-SAVER
(II) Loading extension XFree86-VidModeExtension
(II) Loading extension XFree86-DGA
(II) Loading extension DPMS
(II) Loading extension XVideo
(II) Loading extension XVideo-MotionCompensation
(II) Loading extension X-Resource
(II) LoadModule: “dbe”
(II) Loading /usr/lib/xorg/modules/extensions/libdbe.so
(II) Module dbe: vendor="X.Org Foundation"
compiled for 1.7.7, module version = 1.0.0
Module class: X.Org Server Extension
ABI class: X.Org Server Extension, version 2.0
(II) Loading extension DOUBLE-BUFFER
(II) LoadModule: “glx”
(II) Loading /usr/lib/xorg/modules/extensions/libglx.so
(II) Module glx: vendor="NVIDIA Corporation"
compiled for 4.0.2, module version = 1.0.0
Module class: X.Org Server Extension
(II) NVIDIA GLX Module 290.10 Wed Nov 16 18:01:24 PST 2011
(II) Loading extension GLX
(II) LoadModule: “record”
(II) Loading /usr/lib/xorg/modules/extensions/librecord.so
(II) Module record: vendor="X.Org Foundation"
compiled for 1.7.7, module version = 1.13.0
Module class: X.Org Server Extension
ABI class: X.Org Server Extension, version 2.0
(II) Loading extension RECORD
(II) LoadModule: “dri”
(II) Loading /usr/lib/xorg/modules/extensions/libdri.so
(II) Module dri: vendor="X.Org Foundation"
compiled for 1.7.7, module version = 1.0.0
ABI class: X.Org Server Extension, version 2.0
(II) Loading extension XFree86-DRI
(II) LoadModule: “dri2”
(II) Loading /usr/lib/xorg/modules/extensions/libdri2.so
(II) Module dri2: vendor="X.Org Foundation"
compiled for 1.7.7, module version = 1.1.0
ABI class: X.Org Server Extension, version 2.0
(II) Loading extension DRI2
(II) LoadModule: “nvidia”
(II) Loading /usr/lib/xorg/modules/drivers/nvidia_drv.so
(II) Module nvidia: vendor="NVIDIA Corporation"
compiled for 4.0.2, module version = 1.0.0
Module class: X.Org Video Driver
(II) NVIDIA dlloader X Driver 290.10 Wed Nov 16 17:41:10 PST 2011
(II) NVIDIA Unified Driver for all Supported NVIDIA GPUs
(II) Primary Device is: PCI 02@00:00:0
(II) Loading sub module “fb”
(II) LoadModule: “fb”
(II) Loading /usr/lib/xorg/modules/libfb.so
(II) Module fb: vendor="X.Org Foundation"
compiled for 1.7.7, module version = 1.0.0
ABI class: X.Org ANSI C Emulation, version 0.4
(II) Loading sub module “wfb”
(II) LoadModule: “wfb”
(II) Loading /usr/lib/xorg/modules/libwfb.so
(II) Module wfb: vendor="X.Org Foundation"
compiled for 1.7.7, module version = 1.0.0
ABI class: X.Org ANSI C Emulation, version 0.4
(II) Loading sub module “ramdac”
(II) LoadModule: “ramdac”
(II) Module “ramdac” already built-in
() NVIDIA(0): Depth 24, (–) framebuffer bpp 32
(==) NVIDIA(0): RGB weight 888
(==) NVIDIA(0): Default visual is TrueColor
(==) NVIDIA(0): Using gamma correction (1.0, 1.0, 1.0)
() NVIDIA(0): Option “Coolbits” “1”
() NVIDIA(0): Option “TripleBuffer” “false”
() NVIDIA(0): Option “AddARGBGLXVisuals” “true”
() Mar 10 18:23:27 NVIDIA(0): Enabling 2D acceleration
(WW) Mar 10 18:23:28 NVIDIA(GPU-0): Unable to read EDID for display device CRT-1
(II) Mar 10 18:23:28 NVIDIA(0): NVIDIA GPU GeForce 8400 GS (G98) at PCI:2:0:0 (GPU-0)
(–) Mar 10 18:23:28 NVIDIA(0): Memory: 524288 kBytes
(–) Mar 10 18:23:28 NVIDIA(0): VideoBIOS: 62.98.29.00.41
(II) Mar 10 18:23:28 NVIDIA(0): Detected PCI Express Link width: 16X
(–) Mar 10 18:23:28 NVIDIA(0): Interlaced video modes are supported on this GPU
(–) Mar 10 18:23:28 NVIDIA(0): Connected display device(s) on GeForce 8400 GS at PCI:2:0:0
(–) Mar 10 18:23:28 NVIDIA(0): CRT-1
(–) Mar 10 18:23:28 NVIDIA(0): CRT-1: 400.0 MHz maximum pixel clock
() Mar 10 18:23:28 NVIDIA(0): Using HorizSync/VertRefresh ranges from the EDID has been
() Mar 10 18:23:28 NVIDIA(0): enabled on all display devices.
(II) Mar 10 18:23:28 NVIDIA(0): Assigned Display Device: CRT-1
(WW) Mar 10 18:23:28 NVIDIA(0): No valid modes for “4095x4095”; removing.
(WW) Mar 10 18:23:28 NVIDIA(0): No valid modes for “1280x1024”; removing.
(WW) Mar 10 18:23:28 NVIDIA(0): No valid modes for “1024x768”; removing.
(WW) Mar 10 18:23:28 NVIDIA(0): No valid modes for “832x624”; removing.
(WW) Mar 10 18:23:28 NVIDIA(0): No valid modes for “800x600”; removing.
(WW) Mar 10 18:23:28 NVIDIA(0): No valid modes for “720x400”; removing.
(II) Mar 10 18:23:28 NVIDIA(0): Validated modes:
(II) Mar 10 18:23:28 NVIDIA(0): “640x480”
(II) Mar 10 18:23:28 NVIDIA(0): Virtual screen size determined to be 640 x 480
(WW) Mar 10 18:23:28 NVIDIA(0): Unable to get display device CRT-1’s EDID; cannot compute DPI
(WW) Mar 10 18:23:28 NVIDIA(0): from CRT-1’s EDID.
(==) Mar 10 18:23:28 NVIDIA(0): DPI set to (75, 75); computed from built-in default
() Mar 10 18:23:28 NVIDIA(0): Enabling 32-bit ARGB GLX visuals.
(–) Depth 24 pixmap format is 32 bpp
(II) Mar 10 18:23:28 NVIDIA: Using 768.00 MB of virtual memory for indirect memory access.
(II) Mar 10 18:23:28 NVIDIA(0): Setting mode “640x480”
(II) Mar 10 18:23:28 NVIDIA(0): Built-in logo is bigger than the screen.
(II) Loading extension NV-GLX
(==) NVIDIA(0): Disabling shared memory pixmaps
(==) NVIDIA(0): Backing store disabled
(==) NVIDIA(0): Silken mouse enabled
() NVIDIA(0): DPMS enabled
(II) Loading extension NV-CONTROL
(WW) Mar 10 18:23:28 NVIDIA(0): Option “TwinViewXineramaInfoOrder” requested “DFP”, but no
(WW) Mar 10 18:23:28 NVIDIA(0): such display device could be found, or all display devices
(WW) Mar 10 18:23:28 NVIDIA(0): by that name are currently unavailable.
(WW) Mar 10 18:23:28 NVIDIA(0): Option “TwinViewXineramaInfoOrder” requested “TV”, but no such
(WW) Mar 10 18:23:28 NVIDIA(0): display device could be found, or all display devices by
(WW) Mar 10 18:23:28 NVIDIA(0): that name are currently unavailable.
(II) Loading extension XINERAMA
(WW) NVIDIA(0): Option “IgnoreEDID” is not used
(==) RandR enabled
(II) Initializing built-in extension Generic Event Extension
(II) Initializing built-in extension SHAPE
(II) Initializing built-in extension MIT-SHM
(II) Initializing built-in extension XInputExtension
(II) Initializing built-in extension XTEST
(II) Initializing built-in extension BIG-REQUESTS
(II) Initializing built-in extension SYNC
(II) Initializing built-in extension XKEYBOARD
(II) Initializing built-in extension XC-MISC
(II) Initializing built-in extension SECURITY
(II) Initializing built-in extension XINERAMA
(II) Initializing built-in extension XFIXES
(II) Initializing built-in extension RENDER
(II) Initializing built-in extension RANDR
(II) Initializing built-in extension COMPOSITE
(II) Initializing built-in extension DAMAGE
SELinux: Disabled on system, not enabling in X server
(II) Initializing extension GLX
(II) config/udev: Adding input device Power Button (/dev/input/event2)
() Power Button: Applying InputClass “evdev keyboard catchall”
(II) LoadModule: “evdev”
(II) Loading /usr/lib/xorg/modules/input/evdev_drv.so
(II) Module evdev: vendor="X.Org Foundation"
compiled for 1.7.6.901, module version = 2.3.2
Module class: X.Org XInput Driver
ABI class: X.Org XInput driver, version 7.0
() Power Button: always reports core events
() Power Button: Device: “/dev/input/event2”
(II) Power Button: Found keys
(II) Power Button: Configuring as keyboard
(II) XINPUT: Adding extended input device “Power Button” (type: KEYBOARD)
() Option “xkb_rules” “evdev”
() Option “xkb_model” “pc105”
() Option “xkb_layout” “fr”
() Option “xkb_variant” “latin9”
(II) config/udev: Adding input device Power Button (/dev/input/event1)
() Power Button: Applying InputClass “evdev keyboard catchall”
() Power Button: always reports core events
() Power Button: Device: “/dev/input/event1”
(II) Power Button: Found keys
(II) Power Button: Configuring as keyboard
(II) XINPUT: Adding extended input device “Power Button” (type: KEYBOARD)
() Option “xkb_rules” “evdev”
() Option “xkb_model” “pc105”
() Option “xkb_layout” “fr”
() Option “xkb_variant” “latin9”
(II) config/udev: Adding input device Logitech USB-PS/2 Optical Mouse (/dev/input/event4)
() Logitech USB-PS/2 Optical Mouse: Applying InputClass “evdev pointer catchall”
() Logitech USB-PS/2 Optical Mouse: always reports core events
() Logitech USB-PS/2 Optical Mouse: Device: “/dev/input/event4”
(II) Logitech USB-PS/2 Optical Mouse: Found 3 mouse buttons
(II) Logitech USB-PS/2 Optical Mouse: Found scroll wheel(s)
(II) Logitech USB-PS/2 Optical Mouse: Found relative axes
(II) Logitech USB-PS/2 Optical Mouse: Found x and y relative axes
(II) Logitech USB-PS/2 Optical Mouse: Configuring as mouse
() Logitech USB-PS/2 Optical Mouse: YAxisMapping: buttons 4 and 5
() Logitech USB-PS/2 Optical Mouse: EmulateWheelButton: 4, EmulateWheelInertia: 10, EmulateWheelTimeout: 200
(II) XINPUT: Adding extended input device “Logitech USB-PS/2 Optical Mouse” (type: MOUSE)
(II) Logitech USB-PS/2 Optical Mouse: initialized for relative axes.
(II) config/udev: Adding input device Logitech USB-PS/2 Optical Mouse (/dev/input/mouse1)
(II) No input driver/identifier specified (ignoring)
(II) config/udev: Adding input device HID 04f3:0103 (/dev/input/event6)
() HID 04f3:0103: Applying InputClass “evdev keyboard catchall”
() HID 04f3:0103: always reports core events
() HID 04f3:0103: Device: “/dev/input/event6”
(II) HID 04f3:0103: Found keys
(II) HID 04f3:0103: Configuring as keyboard
(II) XINPUT: Adding extended input device “HID 04f3:0103” (type: KEYBOARD)
() Option “xkb_rules” “evdev”
() Option “xkb_model” “pc105”
() Option “xkb_layout” “fr”
() Option “xkb_variant” “latin9”
(II) config/udev: Adding input device HID 04f3:0103 (/dev/input/event7)
() HID 04f3:0103: Applying InputClass “evdev keyboard catchall”
() HID 04f3:0103: always reports core events
() HID 04f3:0103: Device: “/dev/input/event7”
(II) HID 04f3:0103: Found 1 mouse buttons
(II) HID 04f3:0103: Found scroll wheel(s)
(II) HID 04f3:0103: Found relative axes
(II) HID 04f3:0103: Found absolute axes
(II) HID 04f3:0103: Found keys
(II) HID 04f3:0103: Configuring as mouse
(II) HID 04f3:0103: Configuring as keyboard
() HID 04f3:0103: YAxisMapping: buttons 4 and 5
() HID 04f3:0103: EmulateWheelButton: 4, EmulateWheelInertia: 10, EmulateWheelTimeout: 200
(II) XINPUT: Adding extended input device “HID 04f3:0103” (type: KEYBOARD)
() Option “xkb_rules” “evdev”
() Option “xkb_model” “pc105”
() Option “xkb_layout” “fr”
() Option “xkb_variant” “latin9”
(EE) HID 04f3:0103: failed to initialize for relative axes.
(II) HID 04f3:0103: initialized for absolute axes.
(II) config/udev: Adding input device HDA Digital PCBeep (/dev/input/event5)
(II) No input driver/identifier specified (ignoring)
(II) config/udev: Adding input device PC Speaker (/dev/input/event3)
(II) No input driver/identifier specified (ignoring)
(II) config/udev: Adding input device Macintosh mouse button emulation (/dev/input/event0)
() Macintosh mouse button emulation: Applying InputClass “evdev pointer catchall”
() Macintosh mouse button emulation: always reports core events
() Macintosh mouse button emulation: Device: “/dev/input/event0”
(II) Macintosh mouse button emulation: Found 3 mouse buttons
(II) Macintosh mouse button emulation: Found relative axes
(II) Macintosh mouse button emulation: Found x and y relative axes
(II) Macintosh mouse button emulation: Configuring as mouse
() Macintosh mouse button emulation: YAxisMapping: buttons 4 and 5
(**) Macintosh mouse button emulation: EmulateWheelButton: 4, EmulateWheelInertia: 10, EmulateWheelTimeout: 200
(II) XINPUT: Adding extended input device “Macintosh mouse button emulation” (type: MOUSE)
(II) Macintosh mouse button emulation: initialized for relative axes.
(II) config/udev: Adding input device Macintosh mouse button emulation (/dev/input/mouse0)
(II) No input driver/identifier specified (ignoring)[/code]
Par contre, je ne vois pas de quel ligne des Modes tu parle.