How strange... it appears to work on all pages except for Home.
Home has the image slideshow that the other pages don't have.I don't understand why, but whenever the image "Figurative_Flying" rotates in, my browser shows a left column div appearing over the nav bar area that holds Home and About, keeping About from being clicked on.
Try deleting your slide show block, test, re-install it and add images one at a time.

That is very odd, removing the block does fix it, I have never seen that before

Thanks Adreco,
Deleted the whole block and then reinstated with same images and it works fine now. Very strange, but thanks again.