When I view source of your page, I see the following at the top:
<!-- This page created with ProStores technology. http://www.prostores.com -->
<!-- ProStores technology portions copyright 1997-2009. ProStores, Inc. All Rights Reserved. -->
<!-- Designated trademarks and brands are the property of their respective owners. -->
<html xmlns="http://www.w3.org/1999/xhtml">
there are a couple things wrong here. both of which are causing IE to render in quirls mode which is breaking the menu.
1) There can be no HTML on the page before the <doctype... > tag.
2) You do not have a <doctype..> tag. For standards compliance, you must specify a doctyp for the page as the first tag.
change the top of your page to:
<!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">
<!-- ProStores technology portions copyright 1997-2009. ProStores, Inc. All Rights Reserved. -->
<!-- Designated trademarks and brands are the property of their respective owners. -->