Could be a power supply issue, could be the Video card is going bad.. Could be a lot of things.. but more likely an video card issue. You could do the cheapest thing and try and reinstall the Graphics drivers AND check your (monitor it while playing) temps of the GPU as it could be it is getting way too hot and its damaged.. (had a video card die that did the same thing).. though it was green lines most of the time.. some sometimes with other colors.. ended up being a bad video card.. My card was not over heating though.. just went bad..