Index: meta.php
===================================================================
--- meta.php	(revision 17521)
+++ meta.php	(working copy)
@@ -389,6 +389,7 @@
 		$meta_key = isset( $q['key'] ) ? trim( $q['key'] ) : '';
 		$meta_value = isset( $q['value'] ) ? $q['value'] : '';
 		$meta_compare = isset( $q['compare'] ) ? strtoupper( $q['compare'] ) : '=';
+		$meta_compare = ( !isset( $q['compare'] ) && is_array( $meta_value ) ) ? 'IN' : '=';
 		$meta_type = isset( $q['type'] ) ? strtoupper( $q['type'] ) : 'CHAR';
 
 		if ( ! in_array( $meta_compare, array( '=', '!=', '>', '>=', '<', '<=', 'LIKE', 'NOT LIKE', 'IN', 'NOT IN', 'BETWEEN', 'NOT BETWEEN' ) ) )