Index: _source/plugins/about/plugin.js
===================================================================
--- _source/plugins/about/plugin.js	(revision 3561)
+++ _source/plugins/about/plugin.js	(working copy)
@@ -9,6 +9,7 @@
 	{
 		var command = editor.addCommand( 'about', new CKEDITOR.dialogCommand( 'about' ) );
 		command.modes = { wysiwyg:1, source:1 };
+		command.canUndo = false;
 
 		editor.ui.addButton( 'About',
 			{
Index: _source/plugins/clipboard/plugin.js
===================================================================
--- _source/plugins/clipboard/plugin.js	(revision 3561)
+++ _source/plugins/clipboard/plugin.js	(working copy)
@@ -60,6 +60,7 @@
 	var cutCopyCmd = function( type )
 	{
 		this.type = type;
+		this.canUndo = ( this.type == 'cut' );		// We can't undo copy to clipboard.
 	};
 
 	cutCopyCmd.prototype =
Index: _source/plugins/find/plugin.js
===================================================================
--- _source/plugins/find/plugin.js	(revision 3561)
+++ _source/plugins/find/plugin.js	(working copy)
@@ -13,14 +13,16 @@
 				label : editor.lang.findAndReplace.find,
 				command : 'find'
 			});
-		editor.addCommand( 'find', new CKEDITOR.dialogCommand( 'find' ) );
+		var findCommand = editor.addCommand( 'find', new CKEDITOR.dialogCommand( 'find' ) );
+		findCommand.canUndo = false;
 
 		editor.ui.addButton( 'Replace',
 			{
 				label : editor.lang.findAndReplace.replace,
 				command : 'replace'
 			});
-		editor.addCommand( 'replace', new CKEDITOR.dialogCommand( 'replace' ) );
+		var replaceCommand = editor.addCommand( 'replace', new CKEDITOR.dialogCommand( 'replace' ) );
+		replaceCommand.canUndo = false;
 
 		CKEDITOR.dialog.add( 'find',	this.path + 'dialogs/find.js' );
 		CKEDITOR.dialog.add( 'replace',	this.path + 'dialogs/find.js' );
Index: _source/plugins/maximize/plugin.js
===================================================================
--- _source/plugins/maximize/plugin.js	(revision 3561)
+++ _source/plugins/maximize/plugin.js	(working copy)
@@ -241,7 +241,8 @@
 
 						savedSelection = savedScroll = null;
 						savedState = this.state;
-					}
+					},
+					canUndo : false
 				} );
 
 			editor.ui.addButton( 'Maximize',
Index: _source/plugins/preview/plugin.js
===================================================================
--- _source/plugins/preview/plugin.js	(revision 3561)
+++ _source/plugins/preview/plugin.js	(working copy)
@@ -86,7 +86,8 @@
 	{
 		init : function( editor )
 		{
-			editor.addCommand( pluginName, previewCmd );
+			var command = editor.addCommand( pluginName, previewCmd );
+			command.canUndo = false;
 			editor.ui.addButton( 'Preview',
 				{
 					label : editor.lang.preview,
Index: _source/plugins/print/plugin.js
===================================================================
--- _source/plugins/print/plugin.js	(revision 3561)
+++ _source/plugins/print/plugin.js	(working copy)
@@ -15,6 +15,7 @@
 
 		// Register the command.
 		var command = editor.addCommand( pluginName, CKEDITOR.plugins.print );
+		command.canUndo = false;
 
 		// Register the toolbar button.
 		editor.ui.addButton( 'Print',
Index: _source/plugins/selection/plugin.js
===================================================================
--- _source/plugins/selection/plugin.js	(revision 3561)
+++ _source/plugins/selection/plugin.js	(working copy)
@@ -221,7 +221,8 @@
 					}
 				});
 
-			editor.addCommand( 'selectAll', selectAllCmd );
+			var command = editor.addCommand( 'selectAll', selectAllCmd );
+			command.canUndo = false;
 			editor.ui.addButton( 'SelectAll',
 				{
 					label : editor.lang.selectAll,
Index: _source/plugins/showblocks/plugin.js
===================================================================
--- _source/plugins/showblocks/plugin.js	(revision 3561)
+++ _source/plugins/showblocks/plugin.js	(working copy)
@@ -110,6 +110,7 @@
 		init : function( editor )
 		{
 			var command = editor.addCommand( 'showblocks', commandDefinition );
+			command.canUndo = false;
 
 			if ( editor.config.startupOutlineBlocks )
 				command.setState( CKEDITOR.TRISTATE_ON );