I have the same problem: “Unreal Engine is exiting due to D3D device being lost.” I did all the above written - nothing helped. At me this error appears at opening practically any editor (the Skeletal, particles, a material). Without this it is impossible to work. You can put a cross on the project, which took a lot of time. If there is any solution, I will provide all the data about errors and their reproductions. Sorry, if something is not clear, I translate through Google.link text