You might want to have a look to this:
http://www.sidesofmarch.com/index.php/archive/2007/04/23/an-ie6-compatible-solution-for-hover
                  Roberto Aloi
                   2009-10-09 17:12:01
                
              You might want to have a look to this:
http://www.sidesofmarch.com/index.php/archive/2007/04/23/an-ie6-compatible-solution-for-hover
It seems that the following is not effected in IE6
#topNavigation ul li:hover ul
{
    display: block;
}
Can you give the level 2 UL/LI a css class assignment then create a selector for it?
The :hover pseudoclass is only supported on a elements by IE6, unfortunately.
Check this article for some advice on how to script around the problem.