The menu on this website: http://www.sohtanaka.com/web-design/side-navigation-tooltip-popup-bubble/ ran fine in IE. It was quick and worked fine. On my website however, it ran slooow.
Look for large images that may be loaded. IE doesn’t seem to handle them very well. The background image for my project was 1196×1150. Pretty large… Gotta adjust for the weakest browsers.