Index: wp-admin/css/nav-menu.dev.css
===================================================================
--- wp-admin/css/nav-menu.dev.css	(revision 16267)
+++ wp-admin/css/nav-menu.dev.css	(working copy)
@@ -131,7 +131,7 @@
 		left: 0;
 	}
 	#menu-management .nav-tabs-arrow-right {
-		right: 0;
+		right: 50px;
 		text-align: right;
 	}
 
Index: wp-admin/js/nav-menu.dev.js
===================================================================
--- wp-admin/js/nav-menu.dev.js	(revision 16267)
+++ wp-admin/js/nav-menu.dev.js	(working copy)
@@ -693,7 +693,7 @@
 				marginFluid = api.isRTL ? 'margin-right' : 'margin-left',
 				marginFixed = api.isRTL ? 'margin-left' : 'margin-right',
 				msPerPx = 2;
-
+				
 			/**
 			 * Refreshes the menu tabs.
 			 * Will show and hide arrows where necessary.
@@ -721,13 +721,21 @@
 
 				// Show the arrows only when necessary
 				if( fixedWidth > tabsWidth )
+				{
+					// If the tabs have been scrolled and the arrows disappear, scroll to the beginning of the tabs.
+					css[marginFluid] = '0px';
+					fluid.animate( css, 100, "linear" );
 					arrowLeft.add( arrowRight ).hide();
+				}
 				else
 					arrowLeft.add( arrowRight ).show();
 			}
 
 			$.fn.extend({
 				makeTabVisible : function() {
+					// Don't try to make the menu-add-new tab visible since it's always visible.
+					if (this.hasClass('menu-add-new'))
+						return;
 					var t = this.eq(0), left, right, css = {}, shift = 0;
 
 					if( ! t.length ) return this;
@@ -756,7 +764,10 @@
 
 			// Find the width of all tabs
 			tabs.each(function(){
-				tabsWidth += $(this).outerWidth(true);
+				if ( !$(this).hasClass('menu-add-new'))
+				{
+					tabsWidth += $(this).outerWidth(true);
+				}
 			});
 
 			// Set up fixed margin for overflow, unset padding
@@ -769,6 +780,13 @@
 			arrowRight = $('<div class="nav-tabs-arrow nav-tabs-arrow-right"><a>&raquo;</a></div>');
 			// Attach to the document
 			fixed.wrap('<div class="nav-tabs-nav"/>').parent().prepend( arrowLeft ).append( arrowRight );
+			$('.nav-tabs-nav').css({'margin-right' : '70px'});
+			$('.menu-add-new')
+				.css({
+					'position' : 'absolute',
+					'top' : 0,
+					'right' : 0
+				});
 
 			// Set the menu tabs
 			api.refreshMenuTabs();