Index: wp-includes/wp-db.php
===================================================================
--- wp-includes/wp-db.php	(revision 19030)
+++ wp-includes/wp-db.php	(working copy)
@@ -1197,7 +1197,7 @@
 				$form = '%s';
 			$formatted_fields[] = $form;
 		}
-		$sql = "{$type} INTO `$table` (`" . implode( '`,`', $fields ) . "`) VALUES ('" . implode( "','", $formatted_fields ) . "')";
+		$sql = "{$type} INTO `$table` (`" . implode( '`,`', $fields ) . "`) VALUES (" . implode( ",", $formatted_fields ) . ")";
 		return $this->query( $this->prepare( $sql, $data ) );
 	}