Index: wp-includes/wp-db.php
===================================================================
--- wp-includes/wp-db.php	(revision 4340)
+++ wp-includes/wp-db.php	(working copy)
@@ -123,7 +123,7 @@
 
 	function flush() {
 		$this->last_result = array();
-		$this->col_info = null;
+		$this->col_info = array();
 		$this->last_query = null;
 	}
 
@@ -368,4 +368,4 @@
 
 if ( ! isset($wpdb) )
 	$wpdb = new wpdb(DB_USER, DB_PASSWORD, DB_NAME, DB_HOST);
-?>
\ No newline at end of file
+?>