Hi Kevin, The Superfish demo CSS sets the submenu width on the ul element and has the nested elements to 100% of that. Any horizontal padding should then be set on the anchor elements.
Your menu sets the ul width, then specifically sets the nested li elements to the same width (150px). This would be fine (although not as flexible), except that you then add horizontal padding to those list items which adds to the overall width, making them wider than their parent ul. This will cause the effect you are seeing in IE. Better to use the recommended way of laying out the menus as it is thoroughly tested to avoid a minefield of such problems across a wide variety of browsers. Joel Birch.