Hey,
 
I've an EVGA Titan X on 365.10 drivers, same happens with a factory DP cable and another one I have (same length), G-Sync is enabled, OD is set to Extreme.
 
Only options available in the Nvidia CP is 50 and 60hz, same in Windows display settings. 
 
Monitor's Function Menu, under Information I see:
Information
Resolution             3440x1440
Max Refresh Rate  60 Hz
Mode                    NVIDIA G-SYNC
 
I've tried turning the monitor on/off. I tried forcing a customized resolution via the NVCP with as low as 70hz, no luck, either.
 
I'm not sure what am I doing wrong. Any ideas?
 
Thanks!
 
Edit: Added screenshots: http://cl.ly/1v2r3p3h2I34 and http://cl.ly/0A0a3v3L1F22.