Index: src/wp-includes/js/wp-lists.js
===================================================================
--- src/wp-includes/js/wp-lists.js	(revision 38065)
+++ src/wp-includes/js/wp-lists.js	(working copy)
@@ -160,6 +160,12 @@
 	 * @return {boolean}
 	 */
 	ajaxDel: function( e, s ) {
+
+		// Return if there is already an AJAX request in progress.
+		if ( wpList.xhr && 4 !== wpList.xhr.readyState ) {
+			return false;
+		}
+
 		e = $(e);
 		s = s || {};
 		var list = this, data = wpList.parseData(e,'delete'), element, res, rres;
@@ -225,11 +231,17 @@
 			}
 		};

-		$.ajax( s );
+		wpList.xhr = $.ajax( s );
 		return false;
 	},

 	ajaxDim: function( e, s ) {
+
+		// Return if there is already an AJAX request in progress.
+		if ( wpList.xhr && 4 !== wpList.xhr.readyState ) {
+			return false;
+		}
+
 		if ( $(e).parent().css('display') == 'none' ) // Prevent hidden links from being clicked by hotkeys
 			return false;

@@ -330,7 +342,7 @@
 			}
 		};

-		$.ajax( s );
+		wpList.xhr = $.ajax( s );
 		return false;
 	},