Css horizontal menu staggered in ie

1

My horizontal menu appears to be staggering (stepping down) in IE 7. Also i have a sub menu on the first two buttons, but when rolling over the 2nd button the sub menu just replaces the 1st sub menu. You can view a live version of it here: http://www.bmamedia.com/mvec/test/index.htm

here’s the markup:

    	<div id="nav">
        
        	<ul>
            
            	<li><a href="#">About</a>
                	<ul>
                    	<li><a href="#">drop1</a></li>
                    	<li><a href="#">drop2</a></li>
                    	<li><a href="#">drop3</a></li>
                    	<li><a href="#">drop4</a></li>
                    </ul>
                </li>
                
                <li><a href="#">Services</a>
                	<ul>
                    	<li><a href="#">drop5</a></li>
                    	<li><a href="#">drop6</a></li>
                    	<li><a href="#">drop7</a></li>
                    	<li><a href="#">drop8</a></li>
                    </ul>
                </li>
                
                <li><a href="#">Choose A Contractor</a></li>
                <li><a href="#">Become a Member</a></li>
                <li><a href="#">Training</a></li>
                <li><a href="#">Safety &amp; Guidelines</a></li>
                <li><a href="#">News</a></li>
                <li><a href="#">Contact</a></li>
            </ul>        
        </div>

And the CSS:

#nav{
margin-left:4px;
height:65px;
}

#nav ul{
list-style-type:none;
padding-left:0;
margin-left:0;
}

#nav ul li ul a{
float:none;
display:block;
height:15px;
border-top:1px solid #ffffff;
border-right:none;
}

#nav ul li ul{
display:none;
position:absolute;
margin-top:74px;
}

#nav ul li:hover ul{
display:block;
position:absolute;
margin-top:74px;
}

.nav ul li{
display:inline;
}

#nav a{
font-family:Arial, Helvetica, sans-serif;
background-color:#dd0a12;
font-size:11px;
color:#FFFFFF;
float:left;
width:76px;
height:65px;
text-decoration:none;
padding:5px;
border-right:1px solid #FFFFFF;
}

#nav a:hover{
background:#CCCC00;
}