I just checked the specs on mine (Viewsonic P95f+), and it says that the highest res possible is 2048 x 1536 at 68Hz.
"Displays a maximum resolution of 2048 x 1536 at 68Hz flicker-free refresh rate for easy-on-the-eyes viewing"
Strangely I can't get it to show up in the settings tab. Tried few other drivers too. Unless it's locked in nv4_disp.inf. Will look into that later