error when accessing catalog. please help

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http://forums.oscommerce.com/viewtopic.php?p=227830#227830
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I get an error message when I try to click on anything on the catalog page.  The only thing I have changed is the reference to languages on line 285 (  require(DIR_WS_LANGUAGES . [b]'english.php' [/b]).  This is the error message I recieve:

[quote]Fatal error: Call to a member function on a non-object in /myserver/catalog/includes/application_top.php on line 310[/quote]

Here is the code as it appears in application_top

[quote]// navigation history
  if (tep_session_is_registered('navigation')) {
    if (PHP_VERSION < 4) {
      $broken_navigation = $navigation;
      $navigation = new navigationHistory;
      $navigation->unserialize($broken_navigation);
    }
  } else {
    tep_session_register('navigation');
    $navigation = new navigationHistory;
  }
  [b]$navigation->add_current_page();[/b][/quote]

Bold faced line is line with the error.  Can anyone give me an idea as to how to fix this problem?  Thanks very much.