Tried that doesn't make any difference I am sure it has something to do with IE7 not recognising z-index but fixing it is another matter. Although it seems to me that its something to do with the containing div as when the mouse goes outside that div the menu goes:
<div id="menu-outer"><img src="img/menu.png" alt="menu-background" width="1024" height="60">
<div id="menu-inner">
<?php require_once("CSSMenuWriter/cssmw/menu.php"); ?>
</div>
<div id="searchbox">
<form name="form1" method="post" action="results.php">
<label>
<input name="ai-search" type="text" id="ai-search" onFocus="if(this.value==this.defaultValue) this.value='';" value="Search">
</label>
<label>
<input type="submit" name="Submit-Btn" id="Submit-Btn" value="GO">
</label>
</form>
</div>
</div>