I have a functioning oscommerce website on my current web server (ubuntu 10.4 - inhouse hosted)

I have recently acquired a linode 768 with ubuntu 10.4. I have configures LAMP, and the site worked well, now that I have configured
"Send-only Mail Server with Exim on Ubuntu 10.04 LTS (Lucid)" I now get this error:

Fatal error: Call to a member function add_current_page() on a non-object in /var/www/gandalf.dynamite.net.nz/public/foxes.co.nz/catalog/includes/application_top.php on line 671

Odly enough, this happened a day or 2 ago after I installed suhosin but after uninstalling, it started working again.

suhosin isn't installed on the current web server.

Somehow seems the navigation parameter remains registered so the class is not instantiated.

1. Backup catalog\includes\application_top.php then open it locate this code:

// 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;
  }
  $navigation->add_current_page();

Replace it with this

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