This usually happens when i am around water. I am normally walking around exploring, and then both my monitors (I have two set up but am only using one for minecraft) turn blank (either colors like black white and/or purple) with stripes running down the screen horizontally. If i am listening to music or watching a video, I can still hear the music/video running. I cant do anything to get out of it (ctrl+alt+delete, esc., etc.) besides force shut-down the whole computer. I am not sure if it is because my computter overheats, because sometimes it happens when i barely start playing minecraft. It also happens most of the time when i am walking/swimming in/around water, and happens ALL the time when i use boats to travel, making it really frustrating. It would help a lot if you could help me with this issue. Thanks!