Index: wp-includes/comment.php
===================================================================
--- wp-includes/comment.php	(revision 6599)
+++ wp-includes/comment.php	(working copy)
@@ -199,24 +199,26 @@
  */
 function get_lastcommentmodified($timezone = 'server') {
 	global $cache_lastcommentmodified, $wpdb;
+
+	if ( isset($cache_lastcommentmodified[$timezone]) )
+		return $cache_lastcommentmodified[$timezone];
+
 	$add_seconds_server = date('Z');
-	$now = current_time('mysql', 1);
-	if ( !isset($cache_lastcommentmodified[$timezone]) ) {
-		switch ( strtolower($timezone)) {
-			case 'gmt':
-				$lastcommentmodified = $wpdb->get_var($wpdb->prepare("SELECT comment_date_gmt FROM $wpdb->comments WHERE comment_date_gmt <= %s AND comment_approved = '1' ORDER BY comment_date_gmt DESC LIMIT 1", $now));
-				break;
-			case 'blog':
-				$lastcommentmodified = $wpdb->get_var($wpdb->prepare("SELECT comment_date FROM $wpdb->comments WHERE comment_date_gmt <= %s AND comment_approved = '1' ORDER BY comment_date_gmt DESC LIMIT 1", $now));
-				break;
-			case 'server':
-				$lastcommentmodified = $wpdb->get_var($wpdb->prepare("SELECT DATE_ADD(comment_date_gmt, INTERVAL %s SECOND) FROM $wpdb->comments WHERE comment_date_gmt <= %s AND comment_approved = '1' ORDER BY comment_date_gmt DESC LIMIT 1", $add_seconds_server, $now));
-				break;
-		}
-		$cache_lastcommentmodified[$timezone] = $lastcommentmodified;
-	} else {
-		$lastcommentmodified = $cache_lastcommentmodified[$timezone];
+
+	switch ( strtolower($timezone)) {
+		case 'gmt':
+			$lastcommentmodified = $wpdb->get_var("SELECT comment_date_gmt FROM $wpdb->comments WHERE comment_approved = '1' ORDER BY comment_date_gmt DESC LIMIT 1");
+			break;
+		case 'blog':
+			$lastcommentmodified = $wpdb->get_var("SELECT comment_date FROM $wpdb->comments WHERE comment_approved = '1' ORDER BY comment_date_gmt DESC LIMIT 1");
+			break;
+		case 'server':
+			$lastcommentmodified = $wpdb->get_var($wpdb->prepare("SELECT DATE_ADD(comment_date_gmt, INTERVAL %s SECOND) FROM $wpdb->comments WHERE comment_approved = '1' ORDER BY comment_date_gmt DESC LIMIT 1", $add_seconds_server));
+			break;
 	}
+
+	$cache_lastcommentmodified[$timezone] = $lastcommentmodified;
+
 	return $lastcommentmodified;
 }