Strange Disappearance in IE7-8

[noahsarkive]

My menu works fine in FF and Safari (Win), but exhibits strange behavior in IE7 and 8:

I mouse over the left-most menu and the drop-down appears, but when mousing over the drop-down, the drop-down disappears. All the other horizontal menu items work correctly.

The url is:
http://www.rentonww.com


The a portion of the UL is below.

Any ideas? Thanks,
Noah

<ul id="udm" class="udm">
            <li><a href="Accessories_C8.cfm">Accessories</a>
              <ul>
                <li style="z-index:10000;"><a href="Accessories_C235.cfm">Belts</a> </li>
                <li style="z-index:9900;"><a href="Accessories_C76.cfm">Buckles</a> </li>
                <li style="z-index:9800;"><a href="Accessories_C72.cfm">Mens</a>
                  <ul>
                    <li><a href="Accessories_C204.cfm">Belts</a> </li>
                    <li><a href="Accessories_C203.cfm">Bolos</a> </li>
                    <li><a href="Accessories_C205.cfm">Neckwear</a> </li>
                    <li><a href="Accessories_C207.cfm">Other Jewelry items</a> </li>
                    <li><a href="Accessories_C202.cfm">Ties</a> </li>
                    <li><a href="Accessories_C206.cfm">Wallets</a> </li>
                  </ul>
                </li>
                <li style="z-index:9700;"><a href="Accessories_C75.cfm">Watches</a> </li>
                <li style="z-index:9600;"><a href="Accessories_C74.cfm">Wedding</a>
                  <ul>
                    <li><a href="Accessories_C213.cfm">Rings</a> </li>
                    <li><a href="Accessories_C214.cfm">Wedding Party Items</a> </li>
                  </ul>
                </li>
                <li style="z-index:9500;"><a href="Accessories_C73.cfm">Womens</a>
                  <ul>
                    <li><a href="Accessories_C229.cfm">Earrings </a> </li>
                    <li><a href="Accessories_C228.cfm">Necklaces</a> </li>
                    <li><a href="Accessories_C212.cfm">Other Jewelry Items</a> </li>
                  </ul>
                </li>
              </ul>
            </li>
...
...
</ul>