@tig said: Are the 'lines' really there ? Do you ever get to select them for deletion, or do they appear and vanish at will ? If they are not 'real', then is it then a graphics-card issue ?? What is your GC? Does it have the latest drivers loaded? What are your Preferences > OpenGL settings? Have you try adjusting these and retesting to see if that resolves this issue ? I can't speak for the problem above, but since mine seems similar... The lines were really there, but when you select and delete them they become blue (selection) and won't delete. They stay blue, impossible to "unselect" nor do any other action. It is as if the don't exist anymore, but are still visible. I had the thing with my old "standard" video card as well as with my new HD7870 Joker card... It hasn't happened since SketchUp 2013 though.