This is a very simple example. And it doesn't seem to occur on a larger scale...
With the below example however FF looks great(bar across the screen with mouse over button)
IE6 makes it look like an italicized button with no mouse over...

Code:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
	<head>
		<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
		<title>Untitled Document</title>
	</head>
	<body>
		<link rel='stylesheet' type='text/css' href='ext/resources/css/ext-all.css' />
		<script type='text/javascript' src='ext/yui-utilities.js'></script>
		<script type='text/javascript' src='ext/ext-all.js'></script>
		<script type='text/javascript' src='ext/ext-bridge-yui.js'></script>
		<script type='text/javascript'>
			Test = function(){
				var toolbar;
				return{
					Init:function(){
						toolbar = new Ext.Toolbar(document.body);
						toolbar.add(
							{
					            text:'Test'
			        		}
						);
					}
				}
			}();
			
			Ext.onReady(Test.Init);
		</script>
	</body>
</html>
Again this doesn't occur in my project's usage of the toolbar. I don't know if this might solve some future problems or not. I thought I would share it though..