You need to give more information regarding your : Operating System, GFX card, Computer rig.
Two possible issues. One, you installed new software or updates, and its causing an issue. Two its a hardware problem.
Download CCleaner and uninstall the old drivers.
https://www.piriform.com/ccleaner/download
Go to your graphics providers site, AMD or Nvdia, download the latest drivers and install.
Alternatively your Card could be over heating, check performance while playing games.
I recall a year ago, AMD drivers use to get this 99% bug, where the card would go into overclock mode and overheat thus causing crashed. Only way to solve it for me, during that period, was to revert to 10.4 drivers, which were, 5 versions backwards.
If you are not sure what hardware you have, download these software for future issues.
http://www.cpuid.com/softwares/cpu-z.html