It seem I always have the same problem when I install Ubuntu, the screen resolution tops out at 1024×768. It truns out the problem is caused by Ubuntu not detecting my monitor correctly. Using a Dell E173FP LCD, Ubuntu defaults to 1024×768 CRT. Editing the monitor section of the xorg.conf files to reflect the actual monitor capabilities fixed the problem. This also worked while using the Nvidia drivers, version 185.
The simple fix was to add these lines to the monitor section and reboot.
Identifier "Configured Monitor"
Vertrefresh 56.0 - 65.0
The rest of the xorg.conf file contains the default settings setup during install. The Dell E173FP optimal resolution is 1280×1024 60Hz, but additional modes are also enabled which can be used for larger monitors, such as 1360×768, 1440×900, and 1600×1024.
Open up Nvidia X Server Settings dialog to adjust the resolution, System->Administration->Nvidia X Server Settings. Go to the X Server Display Configuration section, and choose your optimal resolution.