If a thread on Nvidia's forums is any indication, owners of notebooks with GeForce GTX 860M graphics cards have been experiencing system crashes and unresponsive games for the last few weeks. Nvidia has acknowledged the problems with its drivers for GTX 860M-equipped notebooks and issued an updated driver.
The updated driver, version 359.12, will only install on notebooks with a GTX 860M. The release notes only mention a resolution for instability with that card. Downloads for both 32-bit and 64-bit editions of Windows 7 and later are available from Nvidia's website.