Index: /CKEditor/trunk/_source/plugins/dialog/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/dialog/plugin.js	(revision 5529)
+++ /CKEditor/trunk/_source/plugins/dialog/plugin.js	(revision 5530)
@@ -1658,5 +1658,5 @@
 			if ( CKEDITOR.env.ie6Compat )
 			{
-				var coverDoc = coverElement.getChild( 0 ).getFrameDocument();
+				var coverDoc = currentCover.getChild( 0 ).getFrameDocument();
 				coverDoc.on( 'mousemove', mouseMoveHandler, dialog, { part : partName } );
 				coverDoc.on( 'mouseup', mouseUpHandler, dialog, { part : partName } );
@@ -1729,5 +1729,5 @@
 			if ( CKEDITOR.env.ie6Compat )
 			{
-				var coverDoc = coverElement.getChild( 0 ).getFrameDocument();
+				var coverDoc = currentCover.getChild( 0 ).getFrameDocument();
 				coverDoc.removeListener( 'mouseup', mouseUpHandler );
 				coverDoc.removeListener( 'mousemove', mouseMoveHandler );