After much back and forth with nVidia (that ended with them suggesting this was a hardware issue and leaving me to call the manufacturer of the card
). I've discovered that it is INDEED a problem with the nVidia software. I'm not sure at what level this error occurs but there is something about the GTX280 (and probably other chipsets) not playing nice with the Cintiq 21UX. Maybe it's the capability of the Cintiq to output either VGA or Digital signals (there's a switch on the monitor) and the software just doesn't support it. I don't know. What I DO KNOW is that after trying like 4 different nVidia driver packages nothing was working, the only time I received a digital signal was when I rebooted in safe mode. Finally, I went to see if the working driver package I had on XPx64 had a Windows 7 64 bit version... it didn't. BUT there was a 64 bit Vista version for that driver package (it's 178.24 btw). So I figured I had nothing to lose, did a driver sweeper clean and installed the old package and BOOM, everything works perfectly. Full screen games at less than native resolution were no longer scaling down to a small window with a black BG. the signal was crisp and digital, and everything seems to work great!
The main problem I have now is that these drivers are relatively outdated so I'm losing out on the "30-40% performance gain" that nVidia cites in their release notes for newer drivers. I would love it if windows, wacom, and nVidia were able to identify the critical difference between 178.24 and more recent drivers so that those of us on Cintiqs could get the latest drivers to play nice with our monitor.
I hope this post is helpful because I've been scouring for a solution to this problem for a LOOONG time.
To recap here's what I did to get everything running perfectly:
1.) Download the working nVidia software from here: http://www.nvidia.com/object/winvist...8.24_whql.html
2.) Reboot in safe mode
2.) Go to Device Manager and uninstall the display adapter for your vid card
3.) Run driver sweeper to clean out "nVidia display"
4.) Reboot in safe mode
5.) install the driver software
7.) send me an e-mail thanking me profusely for spending hours every day tracking down the working drivers despite little or no help from nVidia