UE4 crashes in material editor

Well I import a .PNG file, all good. And when I place it inside the material editor it crashes. Yes I know 6GB of RAM is lower than the recomended, but I can assure you I have been able to run at max grafics at 30-50FPS and the rendering doesn’t take long.
I have tried using Png, JPG, Tga,Pbm and a few more.
The editor don’t like outside files…