Comment 26 for bug 205093

Hi,
sudo dpkg-reconfigure xserver-xorg does not work for me too.

Instead open your xorg.conf with gedit (or whatever you like) as:

sudo gedit /etc/X11/xorg.conf

and replace the Section "Monitor" with this one taken from the Gentoo Wiki

Section "Monitor"
       # Block type: 2:0 3:fd
       # Block type: 2:0 3:fc
       Identifier "Acer AL2216W"
       VendorName "ACR"
       ModelName "Acer AL2216W"
       # Block type: 2:0 3:fd
       HorizSync 30-82
       VertRefresh 56-76
       # Max dot clock (video bandwidth) 210 MHz
       # Block type: 2:0 3:fc
       # Block type: 2:0 3:ff
       # DPMS capabilities: Active off:yes Suspend:no Standby:no
       Mode "1680x1050" # vfreq 59.954Hz, hfreq 65.290kHz
               DotClock 146.250000
               HTimings 1680 1784 1960 2240
               VTimings 1050 1053 1059 1089
               Flags "+HSync" "-VSync"
       EndMode
       # Block type: 2:0 3:fd
       # Block type: 2:0 3:fc
       # Block type: 2:0 3:ff
EndSection

Then replace the Section "Screen" with this one

Section "Screen"
    Identifier "Screen0"
    Device "Device0"
    Monitor "Acer AL2216W"
    DefaultDepth 24
    SubSection "Display"
      Depth 24
      Modes "1680x1050"
   EndSubSection

having a nvidia card I first launched sudo nvidia-xconfig and then replaced the two sections as explained above

Hope can help