Index: wp-includes/js/wp-ajax-response.js
===================================================================
--- wp-includes/js/wp-ajax-response.js	(revision 23179)
+++ wp-includes/js/wp-ajax-response.js	(working copy)
@@ -50,6 +50,7 @@
 		return true;
 	},
 	invalidateForm: function ( selector ) {
+		jQuery('div.error').hide();
 		return jQuery( selector ).addClass( 'form-invalid' ).find('input:visible').change( function() { jQuery(this).closest('.form-invalid').removeClass( 'form-invalid' ); } );
 	},
 	validateForm: function( selector ) {