Index: wp-includes/js/tinymce/plugins/wordpress/editor_plugin_src.js
===================================================================
--- wp-includes/js/tinymce/plugins/wordpress/editor_plugin_src.js	(revision 23035)
+++ wp-includes/js/tinymce/plugins/wordpress/editor_plugin_src.js	(working copy)
@@ -307,6 +307,11 @@
 					ed.plugins.wordpress._hideButtons();
 			});
 
+			ed.onKeyDown.add(function(ed, e){
+				if ( e.which == tinymce.VK.DELETE || e.which == tinymce.VK.BACKSPACE )
+					ed.plugins.wordpress._hideButtons();
+			});
+
 			closeOnClick = function(e){
 				var id;