Strange Lighting artifact

Hi all,
I’m getting a strange rendering artifact that seems to be showing up with one of my characters. As you can see from the images the female character has some strange boxes flickering by her eye and also in the eye itself. The weird part is it happens in levels i’ve already created, but if i start one from scratch, with nothing in it they look fine. The second image shows a character with the exact same material and eye setup (even uses the same material), but it seems fine. If someone could give me an idea of where to start looking for the problem that would be great!