The problem isn't IE, it's that you have missing images... by default Firefox doesn't show a placeholder for a missing image where as IE and Chrome do...
The files that are missing are:
Code:
http://thedestinationforum.com/forum/images/Styles/Blackend/buttons/search.png
http://thedestinationforum.com/forum/images/Styles/Blackend/buttons/lastpost-right.png
Try and figure out what image it's supposed to be... worst case upload a 1 pixel x 1 pixel blank PNG or sometime with that filename and it will look right, but the right thing to do is to remove the image from the template though.
You also have a 'double url' entered into the icon legend incorrectly
Code:
http://thedestinationforum.com/forum/images/Styles/Blackend/statusicon/http://img713.imageshack.us/i/newpost16.png