DirectX 11 is (unfortunately) only partially supported on the GTS 250. It does not support a few of the more advanced features that DirectX 11 has to offer -- I have a feeling that this is your problem.
To create a new dxdiag.txt, open your start menu and type "dxdiag" into the search. Open it, and at the bottom of the window that opens, click on "Save all information".
Last edited by Nehm89; 27/10/15 10:12 PM.