Lines in HUD don't show up on some computers

I have a HUD class inherited from AHUD. In overridden PostRender() method I draw several lines with DrawLine(). It works ok but for some reason on a few another pc the lines don’t show up. There’s nothing more on HUD so maybe HUD doesn’t show up completely.
Maybe someone has an idea why it’s happening? It’s the simple code: just several DrawLine() and that’s all. And it works for me and some other part of my team.
Also, I using PostRender() because I need to redraw lines in new positions every frame.