diff --git includes/ajax.inc includes/ajax.inc
index 7ef41bc..371ebb2 100644
--- includes/ajax.inc
+++ includes/ajax.inc
@@ -587,12 +587,19 @@ function ajax_pre_render_element($element) {
         $element['#ajax']['event'] = 'blur';
         break;
 
-      case 'radio':
-      case 'checkbox':
       case 'select':
         $element['#ajax']['event'] = 'change';
         break;
 
+      // Note on 'change' versus 'click' events: Ideally we would fire an AJAX
+      // request for radios and checkboxes when they change, instead of every
+      // time they're clicked. Unfortunately, Internet Explorer doesn't fire
+      // change events correctly. For radio and checkbox elements, the change
+      // event fires only on blur (such as when the user clicks outside the form
+      // element). The workaround is to react on the click event instead of the
+      // change event. See http://www.quirksmode.org/dom/events/change.html#t04
+      case 'radio':
+      case 'checkbox':
       case 'link':
         $element['#ajax']['event'] = 'click';
         break;
diff --git misc/ajax.js misc/ajax.js
index a7dc21a..68e5146 100644
--- misc/ajax.js
+++ misc/ajax.js
@@ -250,15 +250,7 @@ Drupal.ajax.prototype.eventResponse = function (element, event) {
     alert("An error occurred while attempting to process " + ajax.options.url + ": " + e.message);
   }
 
-  // For radio/checkbox, allow the default event. On IE, this means letting
-  // it actually check the box.
-  if (typeof element.type != 'undefined' && (element.type == 'checkbox' || element.type == 'radio')) {
-    return true;
-  }
-  else {
-    return false;
-  }
-
+  return false;
 };
 
 /**