One of the joys of testing with IE8 is the added google time that I get to spend hunting down bugs and solutions. If you find something mesbehaving in Redmond’s browser, then the Internet knows about it and has a fix somewhere.
Todays culprit was caused by using jQuery’s fadeIn effect on a div containing text. The way that jQuery has to animate the opacity transition causes the font’s to not be anti-aliased, appearing all rough and blocky during the animation. It’s due to the use of the filter property to affect the opacity, There are a couple of fixes, including hooking into jQuery to alter how the fadeIn/fadeOut/fadeTo effects work, but the simplest solution is to give the element containing the text a background-color.