Index: _source/plugins/menu/plugin.js
===================================================================
--- _source/plugins/menu/plugin.js	(revision 3268)
+++ _source/plugins/menu/plugin.js	(working copy)
@@ -187,7 +187,7 @@
 					var item = items[ i ];
 					if ( lastGroup != item.group )
 					{
-						output.push( '<div class="cke_menuseparator"></div>' );
+						output.push( '<hr class="cke_menuseparator" />' );
 						lastGroup = item.group;
 					}
 
Index: _source/skins/default/menu.css
===================================================================
--- _source/skins/default/menu.css	(revision 3268)
+++ _source/skins/default/menu.css	(working copy)
@@ -71,7 +71,10 @@
 
 .cke_skin_default .cke_menuseparator
 {
+	position:absolute;
 	background-color: #e3e3c7;
+	color: #e3e3c7;	/* IE */
+	width: 100%;
 	height: 2px;
 	filter: alpha(opacity=70); /* IE */
 	opacity: 0.70; /* Safari, Opera and Mozilla */