Upgrading gtk breaks gdm

[Joe Van Dyk <joevandyk gmail com>]

I'm not sure if this is the correct list for this question, so feel
free to tell me to look elsewhere.

I have a Redhat Enterprise 3 machine.  It has Gtk 2.2 on it.  I want
to upgrade Gtk to a more recent version of Gtk (2.8.6).

So, I created RPMs for these:

atk
cairo
gdk-pixbuf
glib2
gtk2
gtk-engines
icon-slicer
libart
libgnomecanvas
libtiff
pango
redhat-artwork
redhat-logos

It seems to work great, except that gdm doesn't seem to work properly.
 It says something like "There seems to already be an X display
running.  Do you want me to try a different display or retry on this
one?".  The gdm logs say the same thing.

Running startx from the command-line works fine.

Anyone have any ideas?  Do I need to get a later gdm?

Thanks!
Joe