Dropdown menu - is not opening while hover

Hello together,

i have a problem with my dropdown menu and try to solve it for some hours.

Problem: When i go over the menu with the mouse, the menu should show up/open but it don't. It only works when i click to the superior menu site. Just don't find the solution.

Details:
Version: 2.8.1
Revision: 1287
Site online: www.bb-gesunde-raumkonzepte.de

The code
index.php

Code:

<div class="header-bottom">


<div id="nav2">
<?php show_menu2(1, SM2_ROOT, SM2_ALL, SM2_All, false, "\n</li>", false, false, false, '<ul id="header_menu" class="menu">'); ?>
</div>
</div>

css:

Code:

/*Drop-down menu*/
.header-bottom {width: auto;display:block;clear:both;border-right:0px solid #000;}

/* Remove List Formattings
~~~~~~~~~~~~~~~~~~~~ */
ul.menu, li.menu {
list-style-type: none;
margin: 0px;
padding: 0px;
}

/* Drop Down menu */

#nav2 {
float: left;
width:950px;
border:none;
background:rgb(225,225,225) url(./img/nav-back-c1.jpg) no-repeat;
color: #b5cc33; font-size:130%;
}

#nav2 ul {
list-style-type:none;
position: relative;
margin: 0;
padding: 0;
width: auto;
}

#nav2 ul li {
float:left;
text-align:center;
}

#nav2 ul li a {
display:block;
height:3.1em;
line-height:3.1em;
padding:0 16px 0 16px;
text-decoration:none;
font-weight:bold;
color: rgb(0,0,0);
}

/* Root Level Link Formatting */
#nav2 ul li a:hover, #nav2 li a:focus {background-color: rgb (0,0,0); text-decoration:none;}
#nav2 li a:active, #nav2 ul li a.active {background-color: rgb (0,0,0); text-decoration:none;}

/* Current page Customisations*/
#nav2 li.menu-current a {background: #b5cc33; color: rgb(0,0,0); }
#nav2 li.menu-current a {font-weight: bold;}

/* 2nd Child menu */
#nav2 .menu li ul {position: absolute; width: 10em; margin: 0; display: none; text-transform: none; border: none; font-size: 100%;}
#nav2 .menu li ul li {width: 10.5em; text-align: left; font-weight: normal; margin: 0; padding: 0; line-height: normal;}
#nav2 .menu li ul a {width: 10em; height:auto; line-height:1.3em; margin-left:-1px; padding:4px 16px 4px 16px; border-left:solid 1px rgb(175,175,175); border-bottom: solid 1px rgb(175,175,175); background-color:#b5cc33; font-weight:normal; color:rgb(0,0,0);}

/* 2nd Child link hover */
#nav2 .menu li ul a:hover {color: rgb(0,0,0); background: #b5cc33; border: 0; color:#fff;}

/* Show and hide */
#nav2 .menu li:hover ul, #nav2 .menu li a:focus ul, #nav2 .menu li.subMenu ul {display: block;}
#nav2 .menu li ul ul {display: none;}
#nav2 .menu li:hover ul ul, #nav2 .menu li.subMenu ul ul {display: none;}
#nav2 .menu li:hover ul, #nav2 .menu li li:hover ul, #nav2 .menu li.subMenu ul, #nav2 .menu li li.subMenu ul {display: block;}

/* 3rd Child Menu Appreances */
#nav2 .menu li ul li ul li a { width: 10em; height:auto; line-height:1.3em; margin-left:0; padding:4px 16px 4px 16px; border-left:solid 1px rgb(175,175,175); border-bottom: solid 1px rgb(175,175,175); background-color:#b5cc33; font-weight:normal; color:rgb(0,0,0);}

/* Positioning the Pop-out Drops */
#nav2 li {position: relative;}

#nav2 ul ul ul {
position: absolute;
top: 1px;
left: 119%;
}

I'm very thankful for help!