Rendering Artifacts?

I’m getting some really strange artifacts with this rendering. Here it is:

If I remove the character the artifact doesn’t show up, if I remove the lockers it doesn’t show up.

I changed the depth of the mirrors and the artifact got smaller, but didn’t disappear. I disabled the mirror and it was still there. I turned the character 90 degrees that it changed position. The artifact isn’t part of the character itself, I’m sure of it because I’ve rendered the character in other scenes and it worked fine.

Any ideas?

Hi, No idea, because your image doesn’t appear on the page ! sorry !o)

Weird, it does for me. Here’s the address of the image: