All systems have fresh Win 8.1 installations.
I am running the 355.60 Driver on all rigs and i am using the 61 build due to best performance for me with that one.
Can you try build 67 please.
Do you have a cudart32_65.dll in the ccminer folder?
Downgrading the driver could increase by 200-300KHASH per 750ti. (Hot tip

)
Don't forget to donate guys.

TWO NICKLES...
I flipped both you and t-nelson a nickle. The work fixing the "ctrl-c" exit, and the "cpu-mining" switch were both significant contributions. The hash rate really went up on my 970s with the "cpu-mining" switch, frm 14.5Mh/s to 16.5 -17Mh/s. My 750ti cards also do better.
Thank you! --scryptr