Go to <CC installaion folder>\Base.rte\Settings.ini and try to set
Code:
   ResolutionX = 1920
   ResolutionY = 1080
   Fullscreen = 1
   NxWindowed = 1
   NxFullscreen = 1
If you're on Vista/7/8 you'll probably have to go to %userporfile%\AppData\Local\VirtualStore\Program Files\Data Realms\Cortex Command\Settings.ini