The authors of the forums module all use the Firefox web browser exclusively, and apparently never, ever fire up Internet Explorer.
Those of you who are using IE probably notice ridiculous slowness and freezes when using the forums here. I have talked to the development team about this, but as I said they are totally clueless about it since they only use Firefox, and the forums are fast in Firefox. So to them, there is no problem.
If you are using IE and the slowness of the forums bothers you, switching to Firefox is going to be the quickest solution. The speed of the forums when browsed through Firefox is just as fast as IE was with the old forums.