The issue also resolves in IE8 without adjusting the css if you specify a DOCTYPE in the HEAD area. i.e:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
You should really add the proper heading to your pages as IE gets a bit temperamental without the DOCTYPE being specified.