Unknown Transparency issues on export

PLEASE HELP!

I have an urgent deadline and have never experienced this before. I have created some icons in illustrator and they display fine when working on them. The colours are all solid and the elements are layered in the right places. However when I export, everythign seems to be overlapping and transparent. I have checked the layer to see if I'd accidentally set it to any transparency effects and I have checked the colour transparency. I don't know what else to do.