Lighten mode

[sundariharmony]

okay, whenever I try to use the lighten mode on a layer, I get these stupid lines running down my icon. I had that on my other computer too, and it makes me very angry. There are a lot of things I want to use the lighten mode for, but I can't because I can't see what it looks like unless I flatten the image.

So, does anyone know how to fix this? I want those dumb lines gone!