I have just had a problem where the icons were not displayed. When I went up and moused over them they came up white so they may have been black before. When I moved the mouse off them they disappeared again.
I scrolled down the paged and when the pop out advert on the right appeared the icons suddenly appeared in grey and everything seems as normal.
Just closed my browser and came back with the same result as above. When I scrolled half way down the index page they showed up as they should - before the pop out advert. I was going slower down the page this time.