Widescreen problems with DX10/11

[i dont know]

I'm not sure if it's actually just because of DX10/11, but right now I can't get some of my games to run in widescreen (1280 x 768)

Basically my problem is this:

- My monitor is actually 1280 x 1024, but since I prefer widescreen, I changed the default resolution to 1280 x 768 (Now the top and bottom parts of my monitor aren't being used).

- Whenever I try to change my game options (Civ5, Saints Row 3, or Just Cause 2) to widescreen, it remains at 1280 x 1024.

- If I run the game in DX9 (only Civ 5 and SR3 give me the option for this), widescreen works (unfortunately I have to sacrifice performance)

Any help would be appreciated!