I hace installed RH6 on a variety of machines and have
experienced a no. of situations where the Gnome desktop
does not atart :

   1. Typing 'startx' as root results in  a warning message
      about the Gnome File Manager running as root.
Clicking
       OK in this widget results in the File manager
      attempting to start. The FM core dumps and the
       warning msgs reappears. One is then stuck in
an              indefinite loop. The desktop icons never
appear.

       THis error can disappear spontaneously when next
       logging in or when changing the screen resolution.

        It can also reappear ...

   2. Booting into runlevel 5 does not always work. The
       nice graphical login screen appears but when
      attempting to login, the screen flashes a couple of
       times and the login screen reappears. I could not
       find any msgs in the system to indicate what the
       problem could be.

       Typing 'startx' from runlevel 3 was OK.

    3. Typing 'startx' resulted in the msg :

       'Authentication' failed.

       Logging out and back in *usually* (but not always)
        fixes this problem. Waiting a while or rebooting
        also fixes the problem. In one severe case, we
        found the directory /var/lock/console was missing.
        recreating the directory fixed the problem.