Well, I'm not sure why Ubuntu, even with the release of Jaunty, does not recognize my 1366x768 widescreen resolution with Nvidia graphic card. After a lot of googling I found the following solution which work with my setup.

1. Install the Nvidia Settings/Drivers by going to Applications --> Add/Remove Application and choose the following:

- Nvidia X Server Settings

- Nvidia binary X.Org driver (version 173 driver)

 

2. Edit the '/etc/X11/xorg.conf' and the following line:

Section "Device"
Identifier "Configured Video Device"
Driver "nvidia"
Option "ModeValidation" "NoWidthAlignmentCheck, NoDFPNativeResolutionCheck"
EndSection

Section "Monitor"
Identifier "Configured Monitor"
EndSection

Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
EndSection

 3. Restart your computer or simply restart the x-server by logging in to tty1 (ctrl+alt+F1) and run the ff:

 /etc/init.d/gdm restart