nVidia Quadro FX 3800 Full Screen Refresh Issue (Precision T5500 w/ 2900W Monitor)

My company's MIS department gave me a new PC yesterday: Dell Precision T5500 running Windows XP Pro 32-bit with an nVidia Quadro FX 3800. The monitor is a Dell 2900W with a maximum/native resolution of 1600x1050. It is exhibiting a peculiar behavior at any resolution higher than the lowest one or two resolutions.

If I select a wallpaper (background) image, the image is confined to the upper left 2/3 of the screen. Windows simply will not stretch or tile it across the entire desktop. It doesn't matter what the original size of the image is. The taskbar stretches across the entire width of the screen like it should. Icons and application windows can be placed anywhere on the screen (as they should be), and windows can be stretched or maximized across the entire screen (as they should be).

When I minimize a window or click on Start, their images remain behind as "artifacts"...but only in the areas of the screen outside of the upper left 2/3. The upper left 2/3 cleans up like it should. I just cannot refresh the entire screen.

If I don't use a wallpaper image, everything appears to work fine, and I can refresh the entire screen. However...

...if I lock my PC or log off, the "artifacts" remain, just as if I had a wallpaper image.

I have tried drivers from version 178.xx to 191.87. They all exhibited the same behavior. I suppose this could be a conflict with another program, but I'm at a loss of where to start. We have tried two different monitors and both VGA and DVI. My MIS department is looking into this as well.

Any help is appreciated. Screen shots with comments are below. If you don't/can't see them, try this link: http://www.fordspace.net/zenphoto/index.php?album=nvidia-refresh-issue. (The gallery seems to be a little buggy.)