Index: modules/locale/locale.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/locale/locale.admin.inc,v
retrieving revision 1.13
diff -u -p -r1.13 locale.admin.inc
--- modules/locale/locale.admin.inc	11 May 2010 10:49:37 -0000	1.13
+++ modules/locale/locale.admin.inc	28 May 2010 23:04:27 -0000
@@ -519,7 +519,7 @@ function _locale_languages_configure_for
   );
 
   $language_providers = $form['#language_providers'];
-  $enabled_providers = variable_get("locale_language_providers_enabled_$type", array());
+  $enabled_providers = variable_get("language_negotiation_$type", array());
   $providers_weight = variable_get("locale_language_providers_weight_$type", array());
 
   // Add missing data to the providers lists.
@@ -527,16 +527,13 @@ function _locale_languages_configure_for
     if (!isset($providers_weight[$id])) {
       $providers_weight[$id] = language_provider_weight($provider);
     }
-    if (!isset($enabled_providers[$id])) {
-      $enabled_providers[$id] = FALSE;
-    }
   }
 
   // Order providers list by weight.
   asort($providers_weight);
 
   foreach ($providers_weight as $id => $weight) {
-    $enabled = $enabled_providers[$id];
+    $enabled = isset($enabled_providers[$id]);
     $provider = $language_providers[$id];
 
     // List the provider only if the current type is defined in its 'types' key.
@@ -665,7 +662,6 @@ function locale_languages_configure_form
     }
 
     language_negotiation_set($type, $negotiation);
-    variable_set("locale_language_providers_enabled_$type", $enabled_providers);
     variable_set("locale_language_providers_weight_$type", $providers_weight);
   }
 
Index: modules/locale/locale.install
===================================================================
RCS file: /cvs/drupal/drupal/modules/locale/locale.install,v
retrieving revision 1.58
diff -u -p -r1.58 locale.install
--- modules/locale/locale.install	1 May 2010 08:12:23 -0000	1.58
+++ modules/locale/locale.install	28 May 2010 23:45:40 -0000
@@ -56,6 +56,15 @@ function locale_update_7001() {
     // LANGUAGE_NEGOTIATION_PATH_DEFAULT.
     case 1:
       $negotiation = array(LOCALE_LANGUAGE_NEGOTIATION_URL);
+      // In Drupal 6 path prefixes are shown for the default language only when
+      // language negotiation is set to LANGUAGE_NEGOTIATION_PATH, while in
+      // Drupal 7 path prefixes are always shown if not empty. Hence we need to
+      // ensure that the default language has an empty prefix to avoid breaking
+      // the site URLs with a prefix that previously was missing.
+      db_update('languages')
+        ->fields(array('prefix' => ''))
+        ->condition('language', language_default()->language)
+        ->execute();
       break;
 
     // LANGUAGE_NEGOTIATION_PATH.
@@ -70,11 +79,23 @@ function locale_update_7001() {
       break;
   }
 
-  // Save new language negotiation options.
+  // Save the new language negotiation options.
   language_negotiation_set(LANGUAGE_TYPE_INTERFACE, array_flip($negotiation));
   language_negotiation_set(LANGUAGE_TYPE_CONTENT, array(LOCALE_LANGUAGE_NEGOTIATION_INTERFACE => 0));
   language_negotiation_set(LANGUAGE_TYPE_URL, array(LOCALE_LANGUAGE_NEGOTIATION_URL => 0));
 
+  // Save admininstration UI settings.
+  $type = LANGUAGE_TYPE_INTERFACE;
+  $provider_weights = array_flip(array_keys(locale_language_negotiation_info()));
+  variable_set("locale_language_providers_weight_$type", $provider_weights);
+
+  // Update language switcher block delta.
+  db_update('block')
+    ->fields(array('delta' => $type))
+    ->condition('module', 'locale')
+    ->condition('delta', 0)
+    ->execute();
+
   // Unset the old language negotiation system variable.
   variable_del('language_negotiation');
 
@@ -124,7 +145,6 @@ function locale_uninstall() {
 
   foreach (language_types() as $type) {
     variable_del("language_negotiation_$type");
-    variable_del("locale_language_providers_enabled_$type");
     variable_del("locale_language_providers_weight_$type");
   }