It seems that Gengo cares WordPress’ cache feature a bit but not entirely.
I don’t know it comes from the fact that the cache feature is disabled by default.

Anyway there must be some bugs on it.

Past days I saw a kind of it on category listing then I gave away the category listing and replaced by SimpleTagging.

After that I noticed that there was similar thing on page listing. I couldn’t throw away this feature. I needed it.

The problem was that the page list block in the sidebar could be empty for all locales but the one visited firstly after cache feature had been enabled or cache for the page listing had expired.

I tried to fix the bug and have done.

I made a function gengo_list_pages(), which is to be replaced by wp_list_pages() in sidebar.php, in general.

<?php
if (!function_exists('gengo_list_pages')) {
function gengo_list_pages($args = '') {
    if (is_array($args)) {
        $r = &$args;
    } else {
        parse_str($args, $r);
    }
    $r = array_merge(array('language' => the_language(true)), $r);
    return wp_list_pages($r);
}
}
?>

There is also a related bug in the core code of WordPress 2.2.1. 

Index: post.php
===================================================================
--- post.php    (revision 3)
+++ post.php    (working copy)
@@ -1070,9 +1070,14 @@
        extract($r, EXTR_SKIP);

        $key = md5( serialize( $r ) );
-       if ( $cache = wp_cache_get( 'get_pages', 'page' ) )
-               if ( isset( $cache[ $key ] ) )
-                       return apply_filters('get_pages', $cache[ $key ], $r );
+       if ( $cache = wp_cache_get( 'get_pages', 'page' ) ) {
+               if ( isset( $cache[ $key ] ) ) {
+                       $pages = apply_filters('get_pages', $cache[ $key ], $r );
+            if ( $pages && ( $child_of || $hierarchical ) )
+                $pages = & get_page_children($child_of, $pages);
+            return $pages;
+        }
+    }

        $inclusions = '';
        if ( !empty($include) ) {