I'm having this problem too. I have an older Sharp LCD TV that's 1366x768 native. Now, here's the weird thing, the TV doesn't advertise that it supports 1366x768 even though it does, so I had to create a custom resolution on XP. So, even though the TV didn't advertise it supported 1366x768 (via EDID I suppose?), on XP, the nVidia Control Panel let me create it and use that resolution and everything worked swimmingly. However, on Windows 7, the nVidia Control Panel won't let me create the custom resolution, it keeps insisting it's not supported. And I suppose technically it isn't supported by the TV because it's not even in the user manual, but like I said, I know it actually is because I used that resolution when I used to use XP.
I was using nVidia
drivers 162.xx on XP and using 190.xx with Windows 7. I tried downgrading to 162.xx with Windows 7 but it won't let me use Aero if I do that so I didn't even bother trying further. Is there any trick in Windows 7 to force a "non-supported" resolution when creating custom resolutions with the nVidia Control Panel?
EDIT: I'm using a DVI-D connection by the way with a nVidia 6200, and the SHARP TV is the LC-37D5U