Index: modules/simpletest/drupal_web_test_case.php
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/drupal_web_test_case.php,v
retrieving revision 1.225
diff -u -p -r1.225 drupal_web_test_case.php
--- modules/simpletest/drupal_web_test_case.php	19 Jul 2010 21:54:46 -0000	1.225
+++ modules/simpletest/drupal_web_test_case.php	29 Jul 2010 02:40:28 -0000
@@ -1184,6 +1184,9 @@ class DrupalWebTestCase extends DrupalTe
     $test_info['in_child_site'] = FALSE;
 
     include_once DRUPAL_ROOT . '/includes/install.inc';
+
+    // Avoid exceptions from t() during install if the current language is not 'en'.
+    $GLOBALS['language']->language = 'en';
     drupal_install_system();
 
     $this->preloadRegistry();