There is a problem with latest NVIDIA GPU driver (382.05 and newer), Kepler-based GPU and old Maxwells. Unfortunately this issue also affects some Vive users and both Steam, and Nvidia know about this problem but we haven't gotten a fix yet.
Currently the only solution is to downgrade GPU driver to version 381.89. Make sure you uninstall your current driver first, as it's described in this link - http://www.nvidia.pl/object/IO_13955.html and then install the 381.89 version. You can find older driver versions for your Windows and GPU here - http://www.nvidia.com/download/find.aspx.