From what I can see it looks like more of a css issue. Your source code shows:
<div class="accordion-menu">
<ul>
<li><a class="activemenu" href="Media" title="Media">MEDIA</a></li>
<ul class="submenu">
<li><a href="Media/Videos" title="Videos">VIDEOS</a></li>
</ul>
</ul>
</div>
and this in your css:
.submenu {
display: none;
}
First you need to adjust your markup so it outputs like this:
<div>
<ul class="accordion-menu">
<li>
<a class="activemenu" href="Media" title="Media">MEDIA</a>
<ul class="submenu">
<li><a href="Media/Videos" title="Videos">VIDEOS</a></li>
</ul>
</li>
</ul>
</div>
and then add this to your css file:
ul.accordion-menu li:hover ul.submenu {
display: block;
}
The video submenu should now show on hover. You will need to do some more work on your css as the menu won't look great by just doing the above.
You should be able to sort any styling issues by reading this tutorial and demo:
http://csswizardry.com/2011/02/creating-a-pure-css-dropdown-menu/