furbster: Fwiffo had the same problem in firefox, and I'm not sure if he has it fixed yet (using a different browser worked for him.)
Things to try:
Reload the page while holding down "shift" key - this forces the page to reload all the graphics again and hopefully the board graphics correctly.
If that does not work, try clearing the browsers cache - this also will remove all the graphics from the page making the browser to re-download the game board graphics.
(hide) If you only look at some of the discussion boards on a regular basis you can add them to your favourite boards list by going to the Board page and clicking "Add to my favourite boards". (pauloaguia) (show all tips)