GUI コンソールにログインできません

Issue

• Basic Server として Red Hat Enterprise Linux 6 をインストールして、yum groupinstall "X Window System" "GNOME Desktop  Environment" を実行し、デフォルトの runlevel を 5 に設定します。
• GUI コンソールからのログイン時に、パスワードを許可して、ログイン画面が再度表示されます。
• "/var/log/gdm/:0-greeter.log" の結果は以下の通りです。

===== :0-greeter.log output

** (<unknown>:10670):DEBUG:Client registered with session manager:/org/gnome/SessionManager/Client1
gnome-session[10645]:WARNING:Could not launch application 'gnome-power-manager.desktop':Unable to start application:Failed to execute child process "gnome-power-manager" (No such file or directory)
** (process:10685):DEBUG:Greeter session pid=10685 display=:0.0 xauthority=/var/run/gdm/auth-for-gdm-oP9SdK/database

(polkit-gnome-authentication-agent-1:10684):GLib-GObject-WARNING **: cannot register existing type _PolkitError'

(polkit-gnome-authentication-agent-1:10684):GLib-CRITICAL \*\*: g\_once\_init\_leave: assertioninitialization_value != 0' failed
Failed to play sound:Not available

** (<unknown>:10670):WARNING **:Failed to send buffer

** (<unknown>:10670):WARNING **:Failed to send buffer
gdm-simple-greeter[10685]:Gtk-WARNING: gtkwidget.c:5460: widget not within a GtkWindow
Window manager warning:Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x1c0002b (Login Wind)
Window manager warning: meta_window_activate called by a pager with a 0 timestamp; the pager needs to be fixed.
gdm-simple-greeter[10685]:WARNING:Default session is not available
Window manager warning:Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x1c0002b (Login Wind)
Window manager warning: meta_window_activate called by a pager with a 0 timestamp; the pager needs to be fixed.
Window manager warning:CurrentTime used to choose focus window; focus window may not be correct.
Window manager warning:Got a request to focus the no_focus_window with a timestamp of 0.  This shouldn't happen!
Window manager warning:Log level 16:Failed to send buffer
Window manager warning:Log level 16:Failed to send buffer