Out Of Range display problem on Lenny x64.

[Rafał Radecki <radecki.rafal@gmail.com>]

I installed Lenny x64. After gdm's start I've got an error on my display:

OUT OF RANGE 90.0 kHz/60Hz

My default /etc/X11/xorg.conf is:

Section "InputDevice"
        Identifier      "Generic Keyboard"
        Driver          "kbd"
        Option          "XkbRules"      "xorg"
        Option          "XkbModel"      "pc105"

        Option          "XkbLayout"     "pl"
EndSection

Section "InputDevice"
        Identifier      "Configured Mouse"
        Driver          "mouse"

EndSection

Section "Device"
        Identifier      "Configured Video Device"
        Option          "UseFBDev"              "true"
EndSection

Section "Monitor"

        Identifier      "Configured Monitor"
EndSection

Section "Screen"
        Identifier      "Default Screen"
        Monitor         "Configured Monitor"      

EndSection

I tried to change refresh rates through adding:
- to section "Monitor":

HorizSync       30 - 83
VertRefresh     56 - 75

- to section "Screen":

DefaultDepth    16
SubSection      "Display"
Depth   16
Modes   "800x600_60.00"
EndSubSection

I restarted then X/gdm but the problem remains:"OUT OF RANGE 90.0 kHz/60Hz".
My display: LG Flatron L1732S
My graphic adapter: Radeon HD4550.

Until now I didn't have the need to learn about X display system so any help (for someone my case may be trivial & I hope so ;) ) would be kindly appreciated.

With regards,
R.