If you've recently updated Internet Explorer and are using it to view the forum pages, you could try seeing if the Compatibility View setting will fix the problem.
Look at the menu bar at the top and click on "Page" to bring up a drop-down menu. About half way down you should see the words "Compatibility View." Click that and reload your pages. Hopefully that will work.
Unlike their opposition, Microsoft don't automatically make their browsers backward compatible so they put this extra feature in to help combat viewing problems with older websites.
