I use PrecisionX 16 to restore the driver without rebooting the system. These are my steps for a card on Windows that has low hash (crashed driver):
1) Start or re-open PrecisionX 16.
2) Turn off K-Boost with the toggle switch (upper right-and corner).
3) Turn on K-Boost with the same toggle switch.
4) Re-select the boost profile that you prefer (important!).
5) Verify that the fan profile and boost settings are again in place, and that temperature is appropriate.
6) Close or minimize PrecisionX 16.
7) Restart miner, it should again have appropriate hash readings for boost/overclock settings.
You may also have to open nVidia control panel and reset the display resolution if your graphics now "look odd". It isn't every time, but frequently I have to reset display resolution for normal graphics. This is for my work computer, Win 7 X64, with a GTX 960 that I mine with when not playing games. The GTX 960 will get 10.6Mh/s on Quark, but if it crashes with a segmentation fault, it will only get 3Mh/s on miner restart. I then perform the steps above and restart the miner.
There is a memory leak somewhere, but I was suspecting poorly programmed flash-media websites, like my local news site. I need to reboot about once a day because of increasing memory bloat. --scryptr
I'm using an ancient ccminer so I'm not sure about the issue but it does sound like a simple soft crash to me when the card reverts back to lower P state with 405 Mhz. That is how my cards crash if I have too high OC on them or set too high intensity or accidentaly mine on the same card with 2 instances. Memory leak would imply a leak of some sort causing excess memory usage and/or slow performance degradation over time.