IE7 z-index problem

Hi There,

I have creted Jquery Flyout menus for Xcart and one product Slider on the right. It works in every browser except the IE7. In IE7 the Menu goes below the slider. See screenshot attached.

HTML for menus are as follow
<CODE>
<ul id="nav" class="side_menu">
<li id="parent"><a title="Diagnostic" href="home.php?cat=287">Diagnostic</a>
      <!--      First Level Categories      -->
                  <ul style="visibility: hidden; display: block;">
                            <li class="last">
                    <a title="Handheld" href="home.php?cat=288">Handheld</a>
                    <!--      Second Level Categories      -->
                                    </li>
                        </ul>
            </li>
</ul>
</CODE>

and CSS is as follows:
li#parent ul{
    z-index: 10000;
}

#nav ul {
    background:#EBECED !important;
    border:1px solid #C8C8C8;
    display:none;
    left:190px;
    padding:5px;
    position:absolute;
    top:0;
    width:180px;
    z-index:99999;
}

I have this running on my local server. I can share screen if needed screenshot is attached herewith.

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<CODE>
<ul id="nav" class="side_menu">
<li id="parent"><a title="Diagnostic" href="home.php?cat=287">Diagnostic</a>
      <!--	First Level Categories	-->
                  <ul style="visibility: hidden; display: block;">
                            <li class="last">
                    <a title="Handheld" href="home.php?cat=288">Handheld</a>
                    <!--	Second Level Categories	-->
                                    </li>
                        </ul>
            </li>
</ul>
</CODE> 
and CSS is as follows:
li#parent ul{
    z-index: 10000;
} 
#nav ul {
    background:#EBECED !important;
    border:1px solid #C8C8C8;
    display:none;
    left:190px;
    padding:5px;
    position:absolute;
    top:0;
    width:180px;
    z-index:99999;
}