I'm having some strange behaviour on one of my Drupal sites. Usually when I'm logged in as admin (uid 1) I can always see and edit nodes even if they are unpublished (makes sense). However on one of my sites I always get redirected to the "page not found"-page (404 redirect) even when i'm logged in as uid 1. Any ideas?? This is a Drupal 5 site (awww).
-Thomas
Since this happens for user 1 as well, it can't be a permission matter, as uid 1 overrides all access controls.
So most likely you have some module installed, that redirect to the 404 page, when users try to access unpublished nodes, instead of returning access denied.
Disclaimer, this is just a guess.
Check for a errant Pathredirect or Pathauto alias under URL Alias or URL Redirects in admin/build. This generally is what happens to me sometimes when working with nodes.
Your .htaccess file may have a problem too. Try turning off clean URLs and see what happens.