Key phrase here is that you said it fails more often after a cold start. Chips can fail very slowly and can show signs of when they mess up when they are cold, but operate normally when they are at running temp, or they run normally when cold and mess up when they are hot. A game and video editing will stress a PC because everything is running all at once so sounds to me like you are suffering a slow hardware failure. Could be the RAM, chipset or graphics card. I am guessing chipset. First things first though, make sure you are not overclocking anything.