[development] global $user unavaialable?

I'm working on implementing a new cas_server module that allows drupal accounts to be used as a single - sign on source. I have a drupal 5 site issues a redirect to a drupal 6 site, and when I redirect to that page I don't find that the $user global is populated. Is there some function or include that I should b calling to make sure that this data is there? Code snippet that isn't returning correct data. global $user if ($user->uid) { drupal_set_message('user logged in'); } else { drupal_set_message('User not logged in'); } Note that if I click on any other link in the drupal page. I show as being logged in, but the redirect to this page does not load the $user variable. Developing against drupal 6.10