black blotchy bump maps on final gather
 

I am trying to render a scene using shaders that i got off a website. I used these because I am not very good at bump mapping and these have good ones. They render fie but when I try and render them with final gather I get huge black pixely blobs on thge image, or sometimes just black. I've encountered this problem before with un bump mapped materials and boosted the irradiance. but this doesn't work with bump mapped materials. any ideas anyone? I'm really stuck! :(