hi jim, welcome to the site
have you modified auth.php at all? all the session logic which would cause the page not to load is in there.
if you have modified it, could you post the code? also, make sure there is nothing, not even white space printed to the screen by the time you include auth.php. session functions are header info and will fail if anything at all is printed to the screen before those scripts are called.
i'm not sure how closely the pages you are implementing this on follow the tutorial, so it is very hard to give you a good answer without seeing some code.