So what you are doing is known as "Overclocking" now you probably set the values much too high causing unstability and will cause drivers to crash and games to sometimes fail. I advise you turn the numbers down as it can damage your GPU and CPU. Search the web for stable overclock numbers and try running benchmarks like Prime95 and 3DMark.
So the main issue is youve over-overclocked. Reduce the values to a lower number and it should be much more stable.