Index: includes/locale.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/locale.inc,v
retrieving revision 1.112
diff -u -F^f -r1.112 locale.inc
--- includes/locale.inc	28 Mar 2007 14:08:21 -0000	1.112
+++ includes/locale.inc	31 Mar 2007 21:16:03 -0000
@@ -95,10 +95,11 @@ function _locale_admin_manage_screen() {
  * Theme the admin langauge manager form.
  */
 function theme_locale_admin_manage_screen($form) {
+  $default = language_default();
   foreach ($form['name'] as $key => $element) {
     // Do not take form control structures.
     if (is_array($element) && element_child($key)) {
-      $rows[] = array(array('data' => drupal_render($form['enabled'][$key]), 'align' => 'center'), check_plain($key), '<strong>'. drupal_render($form['name'][$key]) .'</strong>', drupal_render($form['native'][$key]), drupal_render($form['direction'][$key]), drupal_render($form['site_default'][$key]), drupal_render($form['weight'][$key]), l(t('edit'), 'admin/build/locale/language/edit/'. $key). ($key != 'en' ? ' ' .l(t('delete'), 'admin/build/locale/language/delete/'. $key) : ''));
+      $rows[] = array(array('data' => drupal_render($form['enabled'][$key]), 'align' => 'center'), check_plain($key), '<strong>'. drupal_render($form['name'][$key]) .'</strong>', drupal_render($form['native'][$key]), drupal_render($form['direction'][$key]), drupal_render($form['site_default'][$key]), drupal_render($form['weight'][$key]), l(t('edit'), 'admin/build/locale/language/edit/'. $key). (($key != 'en' && $key != $default->language) ? ' ' .l(t('delete'), 'admin/build/locale/language/delete/'. $key) : ''));
     }
   }
   $header = array(array('data' => t('Enabled')), array('data' => t('Code')), array('data' => t('English name')), array('data' => t('Native name')), array('data' => t('Direction')), array('data' => t('Default')), array('data' => t('Weight')), array('data' => t('Operations')));
Index: modules/locale/locale.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/locale/locale.module,v
retrieving revision 1.163
diff -u -F^f -r1.163 locale.module
--- modules/locale/locale.module	28 Mar 2007 14:08:22 -0000	1.163
+++ modules/locale/locale.module	31 Mar 2007 21:17:20 -0000
@@ -356,6 +356,12 @@ function locale_admin_manage_delete_form
     drupal_set_message(t('The English locale cannot be deleted.'));
     drupal_goto('admin/build/locale/language/overview');
   }
+
+  $default = language_default();
+  if ($default->language == $langcode) {
+    drupal_set_message(t('The default language cannot be deleted.'));
+    drupal_goto('admin/build/locale/language/overview');
+  }
 
   // For other locales, warn user that data loss is ahead.
   $languages = language_list();