Index: wp-includes/wp-db.php
===================================================================
--- wp-includes/wp-db.php	(revision 12531)
+++ wp-includes/wp-db.php	(working copy)
@@ -562,7 +562,7 @@
 			$args = $args[0];
 		$query = str_replace("'%s'", '%s', $query); // in case someone mistakenly already singlequoted it
 		$query = str_replace('"%s"', '%s', $query); // doublequote unquoting
-		$query = str_replace('%s', "'%s'", $query); // quote the strings
+		$query = preg_replace('|(?<!%)%s|', "'%s'", $query); //quote the strings, Avoiding escaped strings
 		array_walk($args, array(&$this, 'escape_by_ref'));
 		return @vsprintf($query, $args);
 	}