Wrong resolution with NEC 2690 and Snow Leopard

I just upgraded from Tiger to Snow Leopard v. 10.6.2 on my MacBook Pro 2.33 Ghz laptop with ATI Radeon X1600 Video Card. I also have a NEC 2690wuxi connected as a 2nd display. After experiencing some color issues, I called NEC tech support, and at one point was directed to reset the display to factory defaults and reinstall Spectraview2 software. After doing so, my NEC will no longer display at the proper 1920 x 1200 resolution, despite that setting being selected in display preferences. It only displays 1600 x 1200 or lower resolution, resulting in a distorted image.

Tech support at NEC suggested I update the ATI Radeon X1600 driver to resolve the issue. But Tech support at ATI/AMD support tells me that this driver must come from Apple. I cannot find an update despite a lot of searching. Any insight into resolving this issue would be appreciated.

Edit: By using the VGA connection on the display with an adapter to connect to my MacBook Pro, I'm able to achieve the proper resolution. Am I loosing anything with this work around?