^ or you just need a good old frying pan or guitar the best to hit them

^ guess your graphics card is overheating

either
1) reduce your graphics settings to a more manageable level (low?, doubt it will actually help much though)
2) as the message mentioned, check your fan whether is running and heatsink properly attached/not covered in dust and your graphics card temperature, processor also if needed). You can use 3rd party program that has stress test function (eg. riva tuner /atitool )to check your graphics card temperature.

By the way, anyone noticed a severe drop in fps especially when got alot of infected bodies outside the safe room door and you open it (pushing all the bodies to the side)