Index: path.module
===================================================================
--- path.module	(revision 137)
+++ path.module	(working copy)
@@ -102,11 +102,9 @@
   }
   else if ($path && $alias) {
     // Check for existing aliases.
-    if ($alias == drupal_get_path_alias($path, $language)) {
+    if (drupal_lookup_path('source', $alias, $language)) {
       // There is already such an alias, neutral or in this language.
-      // Update the alias based on alias; setting the language if not yet done.
-      db_query("UPDATE {url_alias} SET src = '%s', dst = '%s', language = '%s' WHERE dst = '%s'", $path, $alias, $language, $alias);
-    }
+      db_query("UPDATE {url_alias} SET src = '%s' WHERE dst = '%s' AND language = '%s'", $path, $alias, $language);    }
     else {
       // A new alias. Add it to the database.
       db_query("INSERT INTO {url_alias} (src, dst, language) VALUES ('%s', '%s', '%s')", $path, $alias, $language);