Ubuntu – Dual monitor ,not allowed full resolution

I have two monitors, one is connected via HDMI and the other one is connected via a VGA to a DVI adapter. Both of the monitors are 21.5" and support 1920×1080.

The first monitor (HDMI) works just fine in full 1920×1080 resolution. The second monitor says that it supports only 1600×1200, which my monitor only supports 1080 so it doesn't run on it, but it runs just fine on 1600×900, this is how it looks like:

I have tried to manually alter the resolution in xorg.conf but it did not work, it returned back to 1600×900.

I want to use both monitors with the same resolution (1920×1080) in Ubuntu but I don't know how. I am using the latest drivers from the AMD website (not the beta) for my card. I have a ATI RADEON HD 7950 3GB 384 bytes GDDR5.

This is my current xorg.conf:

Section "ServerLayout"
    Identifier     "aticonfig Layout"
    Screen      0  "aticonfig-Screen[0]-0" 0 0
EndSection

Section "Module"
EndSection

Section "Monitor"
    Identifier   "aticonfig-Monitor[0]-0"
    Option      "VendorName" "ATI Proprietary Driver"
    Option      "ModelName" "Generic Autodetecting Monitor"
    Option      "DPMS" "true"
EndSection

Section "Monitor"
    Identifier   "0-DFP5"
    Option      "VendorName" "ATI Proprietary Driver"
    Option      "ModelName" "Generic Autodetecting Monitor"
    Option      "DPMS" "true"
    Option      "PreferredMode" "1920x1080"
    Option      "TargetRefresh" "50"
    Option      "Position" "0 0"
    Option      "Rotate" "normal"
    Option      "Disable" "false"
EndSection

Section "Monitor"
    Identifier   "0-CRT1"
    Option      "VendorName" "ATI Proprietary Driver"
    Option      "ModelName" "Generic Autodetecting Monitor"
    Option      "DPMS" "true"
    Option      "TargetRefresh" "60"
    Option      "Position" "1920 0"
    Option      "Rotate" "normal"
    Option      "Disable" "false"
    Option      "PreferredMode" "1600x900"
EndSection

Section "Device"
    Identifier  "aticonfig-Device[0]-0"
    Driver      "fglrx"
    Option      "Monitor-DFP5" "0-DFP5"
    Option      "Monitor-CRT1" "0-CRT1"
    BusID       "PCI:1:0:0"
EndSection

Section "Screen"
    Identifier "aticonfig-Screen[0]-0"
    Device     "aticonfig-Device[0]-0"
    DefaultDepth     24
    SubSection "Display"
        Modes "1920x1080"
        Viewport   0 0
        Depth     24
    EndSubSection
EndSection

I am using the latest version of Ubuntu, all updates done.

How can I fix this resolution issue?