Widescreen capability not detected

I have a Samsung 906BW 19'' lcd monitor with a native resolution of 1440x900, and a GeForce 8800 GTS 320mb gfx card. All drivers are installed and updated, but windows wouldn't let me choose 1440x900 in settings. So I used the Nvidia control panel to create the resolution, but almost every time it says the resolution test was failed and I can't use it. Sometimes it passes the test, but display is too large for the monitor and I can scroll around my desktop with my mouse. In the Nvidia control panel where it displays information about my monitor, it says the recommended or native resolution is 1024x768. Anyone have this problem, or solved it? Thanks

 

This may seem an odd question but how is the lcd hooked up? VGA, single-link DVI, dual-link DVI, DVI-A, vga to dvi connector? I have seen certain res not being available because of how the monitor is hooked up.