First, reinstall the game this is occurring in--it may fix it. If not, then if you are overclocking--stop. Return system and GPU clocks to default. Wouldn't hurt to reseat the GPU, too--make sure the PCIe contacts are clean and shiny--pencil erasers work well there. Make sure all required power cables are solidly connected--make sure GPU fans are working properly. Last but not least, install the latest drivers and use a display port connection, if your monitor supports it. One more thing, if all of the above fails, try using another cable from GPU to monitor. If all of the above fails, you may need to do an RMA, assuming you are still in the warranty period.
